I manage to get a Zeagle Concept II, fins, mask, regs, 3 mm shorty and a swim suit into a standard roll aboard. This lets me take it carry on at least on most of the bigger jets.
Couple of tricks, first its the fins that get you. They have to fit or be flexible enough to bend (without memory) or short enough, my splits do that very nicely. The BC the trick is to suck the air out of it. Also, mask goes in the fin foot pocket. Computer goes in the other one. Regs get laid out around everything else in a way that keeps them from being pinched or overly squezed. I usually can get my dive lights in as well.
The concept II isn't a small BC, think of it as middle of the road. The trick is to think logically about the space. You need to fill all the empty spaces, also try rotating things you would be surprised how much you can get in a bag.
If I can get a BC in a roll aboard you should be able to get a BP in a bag.
Nice part about carrying it all on, is that I get to go diving no matter what else happens. Now if I can just figure out how to pack my dive tool and to get the TSA not to make me go through screening.
Anyone know if EMT shears can be taken carry on, I've been thinking about moving away from a knife anyway.
Bob