FWIW, All my (tropical), dive gear goes in one carry on backpack:
3mil steamer, reg set, BCD, 2 masks, 2 smallish lights, 2 computers, and DSMB/spool. If I take my F2's and booties they do just fit, but I like my full foot Superchannels, and they go in the checked bag,( too long for the...