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.