That's really cool. I want to see his 2nd version he's planning that will be made out of a solid block of ABS.
I'm no big fan of polymer AR lowers, but it's cool to see someone turning these things out in the garage on a hobbyist level... even cooler to see that it has been tested successfully.
Not to drift the thread, but the "Home Build Projects" section of that forum has some other cool stuff in it too. One of their members is working on a 6.5 Grendel conversion on an SKS.