Just boarded Alaska airlines with a EXO 6400. Cinched down tight with optics, electronics, and some select clothes and no questions from flight attendants or problems fitting in overhead
Flew Delta this past May with a SG 5900 (bivy mode, no lid) and frame as a carry-on. I was hoping I was going to have the bag cinched down pretty small but by the time I put everything in there (sleeping bag, boots, bino harness, and street clothes), it was pretty full, and nobody even looked twice.
I've used my KUIU 5200, but I really like the Venture 2300 for non-checked baggage.. I compresses really small when it needs to, but hold plenty when it has to.. Depending on where I'm going I may/may not use the hip belt, but it makes it nice to be able to use it either way... I carry extra zippered backs that strap on the outside if I need more enclosed space.. Having the space for hydration is nice too.. Good luck with your choice..