Dear Joe and Ken

thanks very much for your interest,it is very important to talk with people that had already make something that you are still planning to do.
this dive is done by using trimix (30%Heliox),I never use aluminium it is more dangerous than the torpedoes!!!
Steel always with four 18lt(4cubic each)two air and two trimix with 20% overfill(aprox 240 bars) for a normal "outside"dive of 20 min bottom time.Decos will be air and pure oxygen in the last two stops.
The problem rises because to enter the sub through a 60cm hatch you have to be a)only in your wet suit(dry suit most probably will be cut and then you will join the crew!),but hypothermia due to Heliox will make things more difficult in such a depth
b)no bcd can be used so you enter naked the sub with carrying only your lights
Trimix supply will be made inside the boat from a 50lt carried all the way down to the control room! from the hatch before the penetration,and for safety you carry a 10lt on your belt.Of course you are alone inside with someone waiting on the conning tower for you to come out.I never use console and spare 2nd stage,in pro diving we use only two small air pressure indicators exactly for the reason you mentioned,and we use two independent first stages from two independent bottles so no need for spares.Did you entered th esub wearing all your gear?How did you manage it through the hatches?
Anyway guys we could talk for this using our private e-mails so don't hesitate to contact me I will be glad to get your opinion.
Still nobody said anything about this hatch on the floor.
Regards
AZ