What size bag for a Greyhound trip?
I'm not a big fan of bus travel, but my stepfather, who travels very infrequently, prefers it over flying. Recently he had to do a long trip from Virginia to Iowa (!), and his choice of conveyance was Greyhound. His bag went underneath the bus. When he finally arrived at his destination, the bag was not there. Fortunately, there hadn't been anything too valuable in it, but he had to replace his clothes and toiletries.
He may choose to travel by bus again. So I'm just wondering, what sort of bag could one be confident of always fitting into the cabin, whether under his seat or in the racks above? (It's been so long since I've taken a long-distance bus trip in the U.S. that I'm not even sure what the interiors look like.) I'd love to get it for him as a gift. Let's assume something soft-sided and not too fussy. He has ZERO technology needs beyond his cellphone. The bag would probably contain a few clothes, basic toiletries, a book or two.
My question is not so much about specific Tom Bihn bags, but rather about shape and sizing. If you use a TB bag as an example to answer the question that's helpful though.