We also dove with Sam's in April - Barrington was our guide for our first three days and he was completely awesome! Our boat had 10-12 divers each day and we were split into 2 groups, on the first day, between nitrox and air divers......later when we were ALL diving nitrox, we were divided between camera people and non camera people.....on another day it was Swiss/nonSwiss! But our group all had pretty much the same air usage rates, 50-60 min is the max anyway - so it worked out fine....
Just a note: Make sure to work on your fitness before heading out and especially before tackling Ulong Channel! The day we did it there were RIPPING currents and we had to work seriously hard to get to the hook spot! One guy ended up hooking much farther back because he couldn't/didn't want to fight to get to the front - back on the boat he said he was really struggling and breathing hard just to get as far as he did!......Cardio fitness is important!
It is definitely an AWESOME dive!