I recently had to deal with an annoying charter captain.
This was an advanced o/w wreck charter.
No technical dives, no penetration, all within sport diving rules.
However a few pairs in the group were technical divers, (myself included) diving with double steel 100's, isolation manifolds reduntant regs & gauges) .
At the safety brieifing the reserve limit was set at 500 psi. In that all divers would surface with at least 500 psi min gauge pressure.
I questioned the captain about the 500 being valid for doubles, & he responded with a hard line " thats the rule" dive by it or don't dive.
I was annoyed with his attitude though, when I pointed out he was requiring the doubles divers to have twice the reserve as singles, he wouldn't listen, didn't care, no discussion.
With an isolation manifold this is not a real problem. Close the crossover. Dive like you have two singles. No biggy or dive the twins down to 500-600 psi, then close the cross over and use the remaining from one tank down to 200 or so, and still show 500 psi reserve. In fact one would finish with the equivalant of 700 psi in a single 100 cu ft tank.
I'm not one who pushes the limits & I ended my 3 rd dive of the day with 600 psi in both tanks, I didn't need to close the crossover to meet the Captain's rule.
However, I'm interested in hearing others opinions.
regards
Mike Dolson