Good morning Ron!
0.120" on the thrust walls, 0.080" on the non-thrust walls, maybe even tolerate 0.075" on a non-thrust wall in a spot here and there, especially if those spots are in the lower portion of the cylinder thats not pounded by the exploding mixture.
That's not a Cleveland thing, that's a universal accepted minimum as far as I know.
Mr DeRyke provided basically the same figures in his article in the December POCA newsletter.
your friend on the DTBB, George