Given Luke's refinements and various electronic solutions, let's set aside practicality for the moment.
Pneumags are not the only marker
Damn. That's a good point. I forgot about that. So even if there was a dump chamber the same size as the piston, the pressure would drop by half (at least)
I didn't know if you were just choosing not to brag, but aren't the OP's concerns the reason you designed the t-rex?
well, that and simplicity's