Since this is the 'non-' part of the site, and tight clearance was mentioned, I once visited a shop in the edge of the Garment District in NYC. It was a loft and I'd somehow winkled out the address. It was called 'Seventrees, Ltd. The owner had developed a cut-down Model 39 S&W pistol in 9 MM and had a government contract to supply them to such as the CIA for 'spy' work. The company was also doing other sorts of highly-concealable weapons such as knives.
A cop of my acquaintance had an 'Asp', as the pistol was called, and I'd shot it a bit.
On a lark, I'd just 'dropped-in' with the idea of, perhaps, buying one of my own. The elevator opened into a cage---they had no interest in my business, except to give me a badly-printed info sheet, and ask me to leave. Interesting experience!
KS