We continually tweak many of the subtleties of our bags -- minor design or material changes that we don't consider ground breaking or even that significant but that, nonetheless, we're eager to implement to continually improve our bags. (You know us: we can't leave well enough alone.) Our goal is to share with you as many of these changes as they happen as possible, but, honestly, there's often many going on simultaneously and it can be difficult to communicate about all of them. Almost all of these minor changes end up making our bags more expensive; when it's a significant increase in expense and we need to raise the price of a bag because of the nudge/tweak/change, we will, of course, let you know in advance.
On the Synapses! After some consideration, we decided that the placement of the shoulder straps on the Synapse 19 and the angle of the shoulder straps on the Synapse 25 could use some nudging. The nudging we came up with for both bags were straps closer to fitting our ideal range of "average" or "ordinary" users. Did we hit that mark? We think we did, though perhaps in better fitting a greater majority of people, a few folks ended up with a pack that fit less well, not better. We certainly take such observations to heart, as similar observations were what lead us to change the straps in the first place.
We have definitely considered offering versions of our packs fitted to more a slight or petite stature; we will continue thinking on this one. Personally: I'm about 5'5", 123lbs, with a moderately petite frame, and all versions of the Synapse 19 have fit me great so far. (Side note: when we make a tweak or a change to our shoulder straps, we'll sew 'em to a pack, load said pack up with weight, and ask different staff of varying heights/builds to try the packs on. We then take a good look at where the straps are hitting them (and, of course, ask them about their experience of their comfort.) Then we hit the trail for some long miles of real-world testing.