The avg piston is so far away from the top, that's not a problem, as long as the head gasket is big enough, same as other long-stroke engines. Unfortunately, it appears the large-bore Aussie gaskets have become difficult to obtain, so the limit is the current ACL @3.55"(-.020"). Printoseals being @3.53"(-.020"). Unlike SBC & BBM, Slanty valves are pretty well centered in the bores, less of an issue.
