Interested in this as well. Trying to wrap up a build now and after using these on other rifles/carbines...its a nice feature especially if you are doing any weak-hand shooting with/manipulation of your AR.
Send hide member - Duffy a PM. I believe he works for BattleArms Development. He helped me out. I don't believe he's a site sponser, but someone who works for BAD isn't an awful second option!