Hi all,
I figured I'd chime in here as I just used one of the new blocks from CSS tonight. It worked perfect, snug fit, and didn't need any extra grinding for fit, even with the Tromix DIY trigger guard (last screw). It all fit together like a glove. I tapped mine for 8x32 screws instead of the 10x32 (like other people have mentioned) mainly cause that's what CSS sold. I even noticed tonight that he's got a pre-tapped internal receiver block up for sale now too.
And before anyone asks; No, I do not work for them, LOL. just a very happy customer.
Mike