Buying 1st SCBA tank - comparing size, fills, & cost

I have a Royale 400 .22 on the way (480 cc CF bottle version). I'm ready to order the tank now and want to check some facts.

So using this calculator and the following values; do these number of calculated fills realistic?

http://www.calc.sikes.us/2/index.php 

Parameters:
PSI pressure rating of tank = 4500
Actual PSI in tank = 4500 
CC of gun's tank = 480
Fill gun to 3190 psi
Fill gun when it gets down to 1960 psi

97 cuft = 19.8 fills
88 cuft = 18 fills
74 cuft = 15.2 fills
71 cuft = 14.6 fills

I have a fire equipment repair company that can fill to 6000 PSI, so I assume doing a true 4500 psi fill should be reasonable (cost = $12/fill).

I'm using the high and low pressures in Steve's shot string here:



So if each fill is good for 100 high-pressure shots, then the difference between the smallest and largest tanks is roughly the equivalent of one tin (~500) of pellets.

Any thoughts or comments on this would be great!