Dave, Thanks for the response. Do you have any sugestions for size of ports (max possible I think) also there appears to be avoid between the inner liner and the outer fiberglass, does this require anything special. I haven't purchased the ports yet but if I understand correctly they have an inner and an outer section which are bolted together once the whole is cut. If these two sections are tightened might they pull the liner in to the outer fiberglass. If they are not tightened sufficiently, mighten the port leak. Thanks in advance. Any recomendations on brands or installation would be appreciated.