I hear you. I should specify that I did not design my own pneumatic mechanism. I took a gun and cut off the feed tube and the handle leaving the trigger mechanism intact. What I did was spend a couple of weeks sculpting a housing to fit snugly around the stripped down gun. The whole thing looks about 90% believable. There is a hole in the top of the barrel for loading, the cocking mechanism in the rear is fairly low profile, and a port in the underside for a remote hose. I figured you could hide that up your sleeve or something.
Did you make a pistol? I've been thinking about it for years, but mostly just a pipe dream. Who knows, if these are well recieved maybe a pistol next.