Think about it- - - -the cylinder volume gets bigger from the overbore, but the combustion chamber stays the same size. That raises the compression pressure unless the piston doesn't go as high in the cylinder. When I was going for max compression on the round track engines I would mill the block deck for zero piston deck height and use a .020" thick steel shim head gasket. Piston/valve clearance, especially with a radical cam, got very critical. Sometimes I had to flycut the valve eyebrows in the pistons deeper.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!