[ksa8907]

At those pressures you would need supercompressibility calculations to more accurately determine how much energy you can put inside your tank.

However, (atmospheric pressure [absolute] + final cng pressure) ÷ (utility base delivery pressure [absolute]) = standard cubic feet per one actual cubic foot.

So a 1 cubic foot tank can store roughly 308 cf at 4500 psig.

I think what you're going to find is that to have a relatively safe and reliable system it will cost more money than it is worth.
Also, what are you going to do with the condensate?