We sell lots of the ProComp rocker covers! Never had any issues. We usually get them without holes for the engines we produce so we can custom locate where the customer wants them( both in back, in the middle, etc). The lip deal to retain the gasket is irrelevant, we glue the gasket to the rocker on everything. We like their heads too, we just won't use any of their parts in them for marine use. TIMINATOR