FX Monsoon question

Just picked up a new / used Monsoon and it is nice. I get 3 & a half mags before it stops cycling. From what I've found, that sounds right.

Anyway, I am wondering if the air cylinder can be removed? Would like to replace with one that has more volume and a pressure gauge.

I know I can get a 45cc extension and a separate gauge, but a couple bucks more and I can just get a larger cylinder.

Anyone here have any advice? How do I degas the cylinder other than shooting it down?