Mystery Ranch Pop Up 28 with their 40L dry bag on the load shelf would be my first choice, especially since both the pack and dry bag can be used as carry on’s.
I’ve been running a Seek Outside Uniweep 4800 with lid and talon which I’m loving as a day pack and back country pack both. Very comfortable with 50 lbs and the base pack is under 4 lbs. plus it’s waterproof.
Only down sides with this pack are they changed from side release buckles to gatekeeper buckles on the new ones and it’s too big for carry a on. You either love the gatekeeper buckles or you hate ‘em, there is no in between. I had a Saker with them and hated ‘em. My oldest boy has a Lanier with ‘em and loves ‘em.
