I use Cometics on my build. The block and heads were decked by me using a 14" cutter head with a CBN carbide cutting disk. Head speed is fixed but I have control over cutting depth and feed speed.
I'm pretty practiced at getting a good finish when the machines not in a bad mood. No idea on the RA. Since I have a 4.1 I counter sink the hell out of the head bolt holes, and do the same to the heads as well. Then when I'm done there I hit the surfaces with a flat diamond honing stone with WD-40 as a lube.
With the Cometics I pop out the rivet and copper coat all 6 sides and my hand. On the hard parts I smear a 1 molecule thick layer or Yamabond around the water ports. Since I have a 4.1 I also drill a pair of steam holes on the exhaust side of the head surface.
What I just described as had a 100 percent success rate with sealing and no fluid leaks. It works so well that I can bust a hyper piston with less than one second of leaning out due to a faulty clogged fuel filter.
It also works with reusing head gaskets. My enigne right now has a pair of used Cometics since I didn't want to wait for some .027"s when I was swapping my 2nd set of busted hypers for my forged slugs.
I don't think the surface finish is the more important factor like a lot of people seem to believe. Flatness is the important thing. If the head bolt holes are pulled up on the block a few thou, that's a deal breaker. If the head has a .004" low area between cylinders or leading to a water port, that's a deal breaker.
MLSs are squishy like composites. If you pull the head down on a raised area of the block, the fire ring does not have the proper clamp pressure, period. Couple that with our 4 bolts per cylinder and it's a recipe for a bunch of ''Cometic gaskets suck'' threads.
