Just got off the phone with Busty, since he can't remember his damn password to access this site, I'll add his knowledge to mine.
Yes, Marcus Neely was the Neel part of MontNeel, Moe Dumont being the other part.
Yes, there was a blow forward being worked on at one point. Originally, it was basically an Automag bolt in a Phantom body, the second version was known as the Legend, but never made it to production. Marcus always had something in the middle of being designed, lot's of ideas, but didn't like to collaborate, so most were never finished. I can remember him showing me a boltless prototype at one point.
Clearly, the Guardian is based on the Falcon, though strangely Marcus always hated the wire detents.
This may have been something he came up with after the whole Falcon deal went belly up. To the best of Busty's recollection, Marcus has a deal with a field in NH called Paintball Heaven. They would finance the development/production of both the Checkmate and the Falcon. In return, they would get half ownership of the Falcon. They were sued for patent infringement over the regulator in the Falcon, can't remember by who, but likely Southern Pneumatics since it was similar to the Phoenix, which Marcus may have also been involved in. The whole thing blew up and Paintball Heaven was quite displeased with Marcus and sent him packing.
This may have been his final project, as last we heard, he had married a rich woman and is living in Florida as a kept man.