It's only there to equalize pressure in the hull and empty and accumulated water. If you are in the states "pipe wrap" tape works much better than gorilla or duct tape as it doesn't leave any residual mastic behind, even a year later. If your somewhere else pipe wrap is like very thick electricical tape. I did this on an old Stellar SR I had that lost the hole cover. Works like a charm and was truer than the original. Just cover and put in a little slice with a razor or knife.
FENN Bluefin S
FENN Swordfish S carbon hybrid
Epic V8 double gen 2
Lot and lots of DK rudders.
Had:
Stellar SEL excel (gen 2)
Stellar SR excel (gen2)
Stellar S18s g1 (excel)
Epic V10 Double (performance)
Stellar SR (gen 1)
V10 sport (gen 2)
V10 (Gen 2)
Beater SEL (gen 1)