Hi, Cherry!
There are two of us--my wife and I--and we take everything save wts. and tanks, too. For years we stowed our regs in our carry-on, but with the acquistion of lots and lots of camera gear, that was no longer possible. So, for the past couple of years we have put our regs in our checked baggage. So far, so good.
However, if we really wanted to, we could put our consols in our carry-ons because they are equiped with quick disconnects. We haven't and, as I wrote earlier, so far so good.
A couple of personal notes are probably in order. We chose, from early on, to buy and take all our own gear. Two major reasons:
(1) It fits correctly,
and
(2) we know it is properly maintained.
There is another less delicate reason, too:
We do not have to worry about its cleanliness. Having seen how some dive shops clean gear after a dive, we want nothing to do with putting a strange mouthpiece in! But you could always put your own on or dip the rental one in a weak bleach solution--surrepticiously, of course!
Hope this helps,
Scorpionfish