When I am doing large scale planning, like you are currently, I use 0.7 cuft/min. That is a little high for the average diver that will be conducting the types of dive you'll be doing, but it also makes it a little more conservative. Chances are if a diver is bailing out, they aren't going to be at their normal 0.5 or below RMV, so 0.7 takes that into consideration.
What it DOESN'T take into consideration is any sort of significant CO2 hit. If your study area is small enough, you might consider staging a good chunk of emergency gas on the bottom, on the line, and at a deco station. You can't carry enough for a big hit, it would have to be staged.
Also, depending on how much physical work you will be doing at depth, you might want to get hold of some people that do actual work at the depths you are talking about on CCR for advise. There aren't very many of them. Diving to 65M and swinging a hammer at 65M are not the same thing.