Large Steel 4500 psi "Cascade" Tanks. Anyone using them?

I was wondering if those large yellow 4500psi "cascade" tanks can be individually filled? And if so, is anyone using this setup as their primary PCP air source? I've seen a few people here use them in combination with a small compressor, but I was thinking more as as primary source and either filling my gun directly or filling an easily portable SCBA tank with them.


 
First off you need a compressor that can fill one without killing it. I have a Sheldon 4.2 that has no issue doing it. I have also filled the green 4500 psi tank with a Alkin W31

I have 2 5000 psi and 1 4500 psi. I use them for air in my garage for testing. I don't have them cascaded. I just use them one at a time. I also have 7 scba tanks for going shooting. Bigbores use a lot of air.
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 ^^^ Thanks,those big yellow ones are the tanks I was wondering about! I'm not really interested in getting a compressor (I don't think I'll shoot enough and need to keep my costs down). I was thinking of getting one of the large tanks and taking it in to have it filled, then leaving it at my home to fill smaller tanks or the gun directly. I know the weight would be an inconvenience, but as much as I plan on shooting I'd rarely ever have to fill it.