Jack, the CCO is this one from LaRue - the M68-CCO:
http://stores.homestead.com/Laruetactical/Detail.bok?no=41
I quizzed Mark LaRue about getting a scope mount that would be at the same height as my Aimpoint. Nope. The easy answer was "use two of the Aimpoint rings". Duh. I was concerned about taking the scope off and on and it holding zero. Mark said "we made our name on return to zero" - the fact I'm using two rings instead of one?
No problems.
As for the center lug, one of my mentors has a bag full (literally, one of those big old-style paper grocery sacks) of broken ARMS rings. His sniper course is difficult to get through with a boltgun, semi-autos don't make it through. When someone shows up with ARMS rings, he pre-emptively tells them to chuck 'em and get some from LaRue.
According to him, no breakages over the years.
My only gripe about LaRue stuff is that the PVS14 mount has the pad in front of the PVS14 objective just a little too high. Wanted to interfere with the occular of the scope - until it got machined down (with the machinist actually)......