Here is my build with Wiseco forged pistons. .0025"-.003" Piston to wall clearance. You can hear a piston slap in this video, it was -15F last night and it is now about 2 degrees. It does not totally go away even when warmed up. It even gets a bit louder depending on colder ambient temps. I was out during -26 temps and it was much louder. Drives me crazy but it is pretty common and not that big of a deal.