Rich,
I'll add this.
That old saying, "it's not how big it is but how you use it"
fits your tank size choice very nicely.
With today's rising fuel costs, it's just as important to understand what your rate of fuel consumption is for your intended use.
Once you know that, you can better judge the tank size you need. Problem is, you need (I guess) the tank right away, which leads to my last pearl of wisdom. :rabbit:
At $10-$12 a gallon construction cost, aluminum air space storage becomes a premium.