Why not just flycut the piston for valve clearance?
I just looked at an 848 head I've got stashed away, and I can see why notching for valve clearance is not an option- - - - - -A large part of the intake valve overhangs the block, not the piston crown! It would be necesary to flycut a big area of the top of the block beside the piston, and blend that area over into the cylinder above the ring travel with a die grinder to obtain any meaningful valve relief. That's the same problem we encountered many years ago on the flathead Ford- - - -a relieved block made for better breathing, but it lowered the compression ratio. There would probably be a net gain in compression pressure with a radically milled head and a relieved block, but it would be pretty labor-intensive and it would involve some pretty sophisticated volume-checking procedures to equalize the size of the dimples cut into the block.
Jerry