list your pony bottle size options / reasons

[DetectorGuy]

Now I am confused!  I have been using the circular NAUI Surface Air Consumption Rate Calculator to check in when I log my dives up till now and thought I should just use this electronic rate calculator to do this from now on as it is very simple to use. When I tried it  and checked against the NAUI calculator there was a huge difference. An example dive was one that Shooter, Art, and I did back on 6-20-09:

118' max depth
68' average depth per both computers (Suunto Vyper and Tusa IQ 700)
80 CF alum with a 19 CF pony (had with but not used)
2600 PSI air used
21 minutes bottom time (this dive was an extreme adrenalin rush for me)
bottom temp was 41 degrees
the visibility varied from 35' to 4' depending on the layer

The NAUI calculator said my sac rate was .40 cu ft per minute
The electronic calculator from the spearfishing website link said my sac rate was 1.07 cu ft per minute.

I haven't taken the time (yet) to do the long hand math to see which is right but I am wondering how I am doing this wrong.