With all deference to Warner, these opinions as to maximum bore size were all believed valid at the time, but largely since the wall didn't actually fail immediately and not all these engines developed enough power to hurt themselves. Jahn's etc. sold many 3/16" and 1/4" O/S pistons to people who "never cleared up that overheating, oil consumption, blowby problem".
Since perhaps 1970, the wall thickness in general and in particular at the thrust surfaces is now known to be much greater than was previously acceptable. This does not include allowance for internal corrosion, core shift, inclusions, etc.
Not enough wall permits the shape to distort under combustion pressure, and makes it difficult for the ring to seal. You get a small amount of extra displacement, but the leak-down rate, oil consumption, crankcase pressurization and ring life are worse - on balance, it's a net loss. Jenkins reported less power from a SBC 350 block at .060" than at .040" for these reasons, and recommended "only enough oversize to clean up and remove any starting chamfer".
I'd try a sonic test of the specific block you're going to use before deciding on a bore size.
