I run R barrels with SP heads with another 0.2 taken off, so 0.4 off stock which leaves a squish of 0.8.

That runs fine 50/50 avgas/95ron unleaded on either a PGMIV c/w HRC 030 card and mc21 flywheel or a stock PGMII.

Dan has o-ringed his NSR (he's done the heads), they're more problems than they're worth.
I've seen ones like this on yahoo Japan, don't know if it works any better or not, same bloke has also got a properly centre plugged head, shame the auction starts at 100,000 yen!
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