list your pony bottle size options / reasons

[jleech]

So to play the \"out of air\" scenario from 130' coming up at 1' every 2 seconds (Not counting the 1 minute half stop at 65' or the 3 minute safety stop at 15' for now) it would take me 4 minutes and 20 seconds to ascend 130'. Now add 4 minutes for the half stop and safety stop, and I would be looking at 8 minutes and 20 seconds to get to the top total time. Round up to 9 minutes to be conservative and my sac rate could be as much as 2.0 cu ft per minute and I would still have a little gas left in a 19 cu ft pony bottle.

Actually, the math is quite a bit more complex than this.  The idea of SAC rate is that it is your "Surface" consumption rate. You need to factor in the additional pressure associated with diving.
Using your example, the easiest math is done like this:
Ascent from 130 to Surface:  4.33 min
Average Depth from 130 to surface = 65ft 
65/33+1=2.97 ATM
4.33*2.97*(SAC rate)= volume of gas used

Deep Stop at 65 ft:  1 min
65/33+1= 2.97 ATM
1*2.97*(SAC rate)=volume of gas used

Safety stop at 15 ft:  3 min
15/33+1= 1.46 ATM
3*1.46*(SAC rate)=volume of gas used

(4.33*2.97)+(2.97*1)+(3*1.46)=(V1+V2+V3)/(SAC Rate)

20.21*(SAC Rate)=volume used

SAC rate=volume used/20.21

If 19 cuft, then SAC rate would need to be 0.94 or less

With an aluminum 80, and a SAC rate of 0.6 cuft/min, you would use 450 psi out of the tank using these numbers, which seems reasonable.