You should be a lawyer.
A G19 will fit in the min dimension box with the 1/4" spacer and it's barrel is less than 4.1". See how easy that was.
The key to gaming the fuck out of this will be to find a gun with a large grip and barrel just under 4.1". I was thinking VP9, but you're right, a 9mm commander with magwell tuned for 125 pf would be the shit yo.
Doesn't someone make a Commander slide on a 2011 frame?