Thanks for the feedback thus far. I forgot to mention, that I already have Li-ions and chargers for the 6P. I have several Q5 modules including DereeLights, and I also have SSC P4 modules and CREE P4 modules from DX.
I hope to find a clicky switch to take advantage of multimode DereeLight modules, and they work fine with forward and reverse clickys. If I can find a hi/low/off two-mode clicky, I might use the one-mode module. The G&P tailcap on LightHound offers strobe, but I don't need this mode. The black HAIII tailcap for the 6PD is almost as much as my entire 6P, so I was hoping to find a cheaper alternative like just changing out the switch. I also considered cannibalizing a Surefire knockoff light from Kai. I have some nice two-mode LumaPower switches that seem to be the right size, but I can't figure out how to remove the momentary switch on the 6P. The momentary on my MRV raps out rather easily, but I can't get the Surefire to budge.
Regarding AR glass, one CPF member reported a increase in 2000 lux in his Q5 MRV knockoff after upgrading from glass to a UCL. This surprised me, but I'm willing to spend another $6 for coated glass if it helps that much.
Thanks again.