adh,
Do yourself a favor and have Gemtech install it for you, otherwise you won't be covered by their warranty. If you let them install it, anything that happens due to the bi-lock will pretty much be covered by Gemtech. If you can afford the M4-96D, you can afford to get the bi-lock from Gemtech and have them install it. It's not worth what you would save by outsourcing it all by another IMHO. By the way, I just back a 11.5" upper with the bi-lock if you care for a picture of that, or check out my picture of an older set up in the general discussion board entitled "Eye Candy".