Stopping the knock: Lower compression and ported heads...

I called the Lunati tech line today. "Mike" said that the most he would advise is .004 over the published .020 & .022 spec. He didn't elaborate on why, just that said not to go beyond that. It was nearing the end of their business hours so I figure that he wanted to cut the call short.
I'm not looking to shred the lobes off here. I'm curious as to how the Mopar Performance solid cams run a .028 & .032 lash without problems. Maybe they have less agressive ramps or something?
I'm still considering the 4 degree cam advance. There seems to be no downside since my piston to valve clearance was over .200 with the .039 head gasket and .236 with the thicker Cometics. I may still run a bit more lash, not sure.