Things to fit things in
I was playing around with some of my Tom Bihn bags and other accessories, and thought I'd note some of the possibly lesser-known combinations that I've found.
First, the Camera I/O fits perfectly within a Pelican 1500 hard case:
And here are some others, though without pictures:
As I mentioned elsewhere, the Smart Alec's Lower Modular Pocket clips into the annex loops in a Brain Bag, or a Smart Alec.
The Upper Modular Pocket, when empty, fits within the Lower Modular Pocket.
The internal dimensions of the Upper Modular Pocket are nearly identical to a Size 2 Stuff Sack, and so you can imagine that one of those fits beautifully there.
The Maxpedition Fatty Organizer fits easily within the Lower Modular Pocket. It will even fits inside the Upper Modular Pocket!
A travel tray folded down fits nicely within an Upper Modular Pocket.
The Co-pilot fits easily into the Brain Bag's first compartment, either horizontally or vertically.
Lots of things besides cameras will fit in a Camera I/O! It effectively adds a padded compartment to your Brain Bag.
3D Organizer cubes fit perfectly inside the "kangaroo pouch" found in the Smart Alec. This is now the dedicated location for my emergency medical kit, tethered by a 16" strap of the same color so that it's easy to pull out when needed.
3D Organizer cubes also fit very nicely into either of the side pockets of the Co-Pilot.
Small organizer pouches fits nicely into the two pockets inside the larger compartment of the Co-pilot.
5" flashlights, like my Eagletac P20C2, sit comfortably either at the bottom of the organizer pocket on the Smart Alec, or in one of the inner pockets of the Upper Modular Pocket.
The Hydroflask 24oz steel bottle fits in the Smart Alec's water bottle pocket as if it was made for it. It also fits nicely in the outside water bottle holder of the Brain Bag.
Have others found any interesting combinations?
Inside a Swift: The medium OP fits nicely into the clear pockets.. The PCSB fits well in the main part. A 500-mL water bottle tucks nicely into the "hidden" pockets inside, though I loop a key strap with both ends attached to the o-ring around it to keep it upright.
Inside an S19: The micro OP (the mystery gift size) fits very, very nicely in the small front pocket, and clips on to the o-ring inside. The pocket pouch fits nicely into the side pockets and can also clip in. 3D org cubes fit well in the bottom pocket; I can get my SE into that pocket but I don't really like it. The PCSB fits well in the main compartment with a SE vertically beside it and a small YSS on top.
Inside an Ego: A Laptop Lunches box fits well, especially if stood on end. The PCSB is a good fit stood on end. A large OP is a good fit but tends to slouch. The SE fits well in the front pocket but makes the bag kind of barrel-shaped. A small OP fits into the zippered front pockets. Bus tickets fit well and are very accessible in the mesh pockets.
Inside an Aeronaut: A full large packing cube (or two smalls) plus a not-too-full Swift or S19 fit well with some space left over. An LCB, even full, will also work and leave more leftover space.
Inside a CQPC: The small OP fits nicely. The pen/pencil OP fits but the end has to be curled up a bit. You can keep about 10 fixed circular knitting needles in their packages in one side (more if you are willing to cram). 8" DPNs fit, but slightly shorter is better.
Inside a Guide's Pack,
A right or left side pocket used as a packing cube fits perfectly laying down across the bottom of the pack.
(A 3d cube and side effect work very well inside either pocket.)
The then stiffness of the side pocket works very well in keeping the pack in a good form.
A PCSB on top of the side pocket laying down or two side by side also work well.
The FJN works very well in the top lid pocket or four 3d cubes or two side effects.
@jwiegley You might be interested in the Going marsupial! TB bags that fit inside other TB bags thread. I tend to answer specific questions about bag usage and link back to this thread in my answers, rather than adding to it though, for example, in the case of answering questions like What are the best organization accessories for a Synapse 19?.
The Co-Pilot also fits into Synapse 25 and Smart Alec. Although I could drop a Co-Pilot that was not heavily stuffed into a Synapse 19 (not so practical since it takes up a good deal of the space), I'd probably rotate it 90 degrees to make it it easier to pull out. You could also stick a Co-Pilot into the middle compartment of a Tri-Star and, of course, a Pilot will also fit there as shown in the picture in the linked post. I typically drop my Little Swift into the center compartment of the Tri-Star when traveling. The Small Cafe Bag will fit into either front pocket of the Western Flyer.
More frequently, we get questions about which packing cubes (Tom Bihn, Eagle Creek, etc.) fit into the various bags, as in the Packing Cubes for Co-Pilot thread (which shows a packed Co-Pilot -- the same one I tried dropping into the Synapse 25 and Smart Alec). That's a whole separate category of questions, with many related threads. And quite a lot of the answers, such as combinations for the Pilot, are buried inside long threads. Usually, it's harder to find the threads that also include pictures that demonstrate the points, like Terayon's pictures of different Aeronaut cubes both outside and inside a Synapse 19 in the Perfect Packing Cube for S19 thread, or Darcy's pictures of Western Flyer cubes in the How to Pack a Smart Alec thread.
I'll break out a separate thread for the Pilot packing options.
An empty Swift packed into an Aeronaut is also perfectly sized for the opening. If you have packed contents and add the flattened bag as a final item, it will not only keep contents from bulging, but is just sized so that the bag's shape covers the opening. Before ther were portable Shop Bags, I used to always add my LUX (Swift predecessor in Ballistic Nylon) as the final item before zipping up my Aeronaut (assuming that I wanted it as a general purpose carrying bag at my destination, and was not already using it as a personal carry-on item while traveling.
Originally Posted by terayon
Off the top of my head, from other threads and my own experimentation:
A Pilot or Cadet will fit into the middle section of a Tristar (my Zephyr with laptop will fit as well but it is tight)
A Pilot will fit into an Aeronaut.
The Aeronaut will also fit a Camera I/IO as well as a Horizontal Brain Cell size 3S (at the same time) and are like padded packing cubes.
Most sizes of Brain Cells will fit into an Aeronaut - the larger ones may need one of the end pocket snap button dividers unsnapped.
A Guide's Pack Lead's Pocket fits into a Brain Bag using the Annex clips.
The Guide's Pack Lead's Pocket also fits the bottom of my Smart Alec perfectly. This is how I currently use it. It also fits vertically in the exterior tie-downs and adds a few more Cu In to what I can carry.
In fact, I really like the Lead's Pocket as I can use it as a pouch, a shoulder bag and a waist bag with the appropriate attachments to the back webbing - very much like a Side Effect of Packing Cube Shoulder Bag (which can also fit in most TB bags).
The Camera I/O fits into both Tri-Star and Aeronaut Packing Cube Back Packs and converts them into a minimalist padded backpack with more structure. You could use a 3S Brain Cell as well (not sure if it is still made).
I love the ideas that everyone brings to the forum for their "bag in a bag" setups - very innovative and useful. I originally wanted TB bags because I could use my Brain Cell in my backpack as well as on its own - a bag in a bag.