Good to know the Cav Arms MkII is back in production. I have heard that those "Glow in the Dark, also called Moonglow" lowers go for some very high prices when they come up for auction. Both of my lowers are of the MKII configuration, one runs a .458 SOCOM upper and the other is a .300 Blackout. Strangely, the lowers come with the receiver pins, or speed pins. Any LPK will work with these lowers, but you will have parts left over. The cassette style triggers also work well in these lowers. If you want to modify, or otherwise make changes to these lowers, Bondo is the material to use. I felt that the magazines were a little loose in the mag well and just added some Bondo to the front of the mag well and used a file to give it a nice tight (but still drops free) fit. I use Krylon Fusion spray paint to touch it up. This stuff works better that Duracoat on poly. I was thinking about making the pistol grip fully customized using Bondo, but then I discovered the Hogue Handall. A little liquid soap on the inside of the Handall, slide it on and rinse off with water. In the last few years I have never had it move around on me. And it works like it was made for this lower.
I read through the history of the CAV Arms lower receivers in the articles you posted and I was a little surprised that there was no mention of the special run called "CAV AID 2008" with that lightly embossed along with a CAV AID serial number (not the actual serial number but the limited run number) on the right side of the magazine well. This run was made by "friends" of Cavalry Arms to help raise money for their legal defense. I have No. 268.
One of the articles says these lowers are best suited for the pencil barreled, lightweight uppers, but I beg to differ. They really come into their own with SBRs, reminding me of some of the sub-guns from WWII and I will tell you that one set up with a .45 ACP SBR upper is what first caught my attention. And they are also like the 1911 in that they seem to multiply overtime. A 10" barreled SBR in .300 Blackout with a pistol silencer would be something special.
One other thing, someone mentioned the Cav Arms butt pads and having no metal support. It has been a while since I have pulled mine off, but I seem to remember that it had a hard plastic 1/4" thick insert in the butt pad, so there was no need for a metal plate. Recoil itself with these thermal plastic lowers is a little less than with a regular aluminium lower, most probably due to the "give" in the plastic. For whatever reason, my .458 SOCOM kicks like a good little 20 gauge gas auto and not the shoulder bruising thumper the .458 SOCOM has a rep for being.
Darn, I already have 3 ARs and now you tell me the CAV Arms MKII is back in production.