I don't need to do the math (although I can do it and do run my rock bottom spread sheet for planing).
I have done wreck ally multiple times, always solo, always with a 13 cu ft pony. Its a hard bottom, the biggest issue is it can be cold and you have currents, so that can surprise some divers. Awesome dives.
I have practiced using a 6 cu ft bottle from 75ft more times than I can count (admittedly in 60F) and I like it for travel. My drills use 1/2 the bottle to get to s/s.
Its not the best tool over 80', you can make it work but you need to understand its limits. (Any tool can be the right tool, just measure once & hammer into place
). The key if you play with the numbers is you must start you ascent immediately and proceed at 60FPM to 60', then 30FPM to the surface. If you waste even a minute at depth, your done for. There is no margin for a partially filled bottle, there is no margin for fiddling around at depth. There is a possibility you do a s/s it may get cut short with a 2nd OOA. If you don't drill enough to ascend immediately or you insist on deep stops or you want a slow ascent or you want padding find something bigger.
---------- Post added March 24th, 2013 at 03:18 PM ----------
Hang on to it. Sooner or later you may find the 6 an ideal size for a travel bottle. While bigger tends to be better, you can very quickly get to the point where you don't dive with the big one because of the hassle factor when traveling. IMO, diving with a small redundant air source is safer than diving without one because you left it at home. Just understand what its limits are and practice often.