OK, while I have been keeping up with this thread, I have slept since then, and I simply do not recall whether the broken cylinders were all on engines where the electric starter was used.
Does anyone remember: are there guys out there that have NEVER used an electric starter and still broke a cylinder?
Is it always #2 cylinder?
How many broken cylinders do we have record of so far?
There might be clues to the failures if we can find some correlations.