Some thoughts on the changing landscape:
10 years ago the standard thing on the forum was getting a 6P, less commonly 9P and getting it bored to 18m for performance stuff and of course there was a number of aftermarket 6p bodies, primarily FiveMega and Leef at the time.
When Malkoff came up with the MD* format lights - not sure of the precise timeline - he kind of made that obsolete. When he came up with heads that outdid anything you could do with the 6P platform, the OEM 6P became irrelevant. Why buy a P60 module when you can just buy a M61HOT? or M61T? I will probably never buy a 6P again for modding. If you want a basic EDC light, you get a regular MD2 with something like M61LL in it, that's already bored for 18mm, or if you want some horsepower you can climb up the M61T / M61HOT / M91 and of course the 18650 Hound Dog ladder which also runs off MD2 body and you can swap between 18650 HD and M61T for example, or some low powered head.
I do wonder if Malkoff contributed to Surefire's 6P demise. In the sense that they went to the sealed head that wasn't possible to unscrew open and mod anymore.
I questioned Malkoff's decision from the start to use MD* heads that were not compatible with Surefire C/C bodies but as it turns out long-term was exactly the correct decision and the right way to adapt to the changing landscape, since C/C has become irrelevant, or nearly so - it's on its way to irrelevance. Yeah, I know many here have surefire 6P and clones but they apparently haven't been sold to the public for years, being incans.