Well...Staying true to my nature of not being able to leave damn well enough alone;
I went and found a "minimalist" magwell for the Compact grip module. This is the ANR Designs ANVL magwell and base pad for the P320. They say it will fit the standard Fullsize, Carry, and Compact grip modules with the Medium grip circumference. Attached by press-fit and retains with a screw through the lanyard hole in the backstrap of the grip module. Unlike other magwells on the market, this one requires no permanent modification to your grip module and is easily removable by removing the set screw.
You can see here the magwell only adds about 1/8-1/4" of length to the bottom of the rear of the grip module, which should allow it to remain fairly concealable. A comparison of the height of the two grip modules;
And where they both sit in my hand;
I've only just received and installed this new part so I will have to do further testing but so far I like how it helps my grip stay in place on the Compact grip module and gives my pinky finger something more substantial to leverage against. I will of course be testing this new addition thoroughly both at the range and for how well it conceals over the next couple of weeks and will report back with any issues or observations.
Of note, the basepad to be used with the magwell does not extend the capacity of the magazine (in this case, 15 rounds); it just replaces the factory plastic basepad which does not work with the ANVL magwell
