I posted in one of the Ciener threads. Try a search for "Essayons" with the "reply author" box checked. If that doesn't work, search the archives. It's out there.
Basically, you need to open up the gap between the lips so the bolt will clear as noted above. You also need to "tap" or "bash" the back of the lips forward until the bolt no longer hits them (or extend the cuts in the bottom of the bolt to provide clearance).
I wish I'd just bought DPMS in the first place, but I wanted the high-cap mag option the Ciener mod provided. It can be difficult-to-impossible to get CZ V22 parts. First I tried to get parts through my vendor. They referred me to
Adco Sales (
NOT ADCO Firearms). Adco sales referred me to
CZ Strojirna (
NOT CZUB/CZ-USA) and they have never responded. I know at least one member has scored spare parts, but so far I haven't.