: We have to make six openings so if there is
: any info on this it would help us on time to have an option of
: some sort of pre-fab.

since you are in the design phase, make all the openings the same size (but 1/8" larger radius) and shape as one of your (or the others) plastic yak coamings. Mask off the plastic yak coaming with saran wrap (and tape) and get one of your helpers to layup a coaming 6 times while all the other work gets done on the main boat by the 5 other guys, etc.
Then glue and glass on these prefabbed (but by you) perfectly sized coamings. If fairly well masked, the plastic yak will not be harmed. If it is harmed, it'll have a stronger coaming, heh heh.