.007"-.008" on Forged piston, race motor.... run it, it will be fine, might slap a little more on cold start but other than that, you'll never know.

I agree with several others that skirt coating is kind of a joke/$ making scheme. Piston top (thermal)coating is about only one worth ever thinking about.

I had a W2 dirt track motor come in shop late last week, guy had 2 spare new pistons for it (JE's) & I saw it had some "home" coated skirts... I mentioned to him, I'm sure that coating probably did'nt survive too well as it's kind of a gimmick, & was a waste of time. Got motor apart & sure enough, not much black coating left on any of the skirts, pretty much completely wore off & that is short stroke long rod piece (3.578" Stroke, 6.40" rod)

See it all the time, even with well done factory coatings by Companies like Mahle & Wiseco on their Pro-Tru's... it just does'nt live forever & is more of a sales ploy than anything.