When I bought my Bavaria 32 2002 she had been laid up unused for about five years.
She was mostly fine but the head waste seacock was badly siezed. I tried penetrating oil leaving the oil to soak plus tapping it but all to no avail.
Due to this I removed the skin fitting. I am about to install a holding tank and intend delivering the waste out from a different position on the boat using another seacock.
I have repaired boats using polyester resin and glass but never below the waterline. Does anyone have any experience of the lay up on these boats as I do not want to use incompatible materials in plugging the hole.
Straightforward solid polyester GRP below the waterline, foam cored above. Good advice on how to do fibreglass repairs on www.westsystem.com
Consider using a Y valve rather than another seacock and skin fitting.