I will be putting two trunks in the transom for when the proverbial hits, one either side of the knees.
The bung idea is just to drain the water that will gather in the sump when the boat is on the trailer outside, if I get water under the deck il not be able to shift it unless I can get it away through transom.
There will be a bilge pump fitted in the sump but I don't want it left in there over the winter where its liable to crack when the water in sump freezes solid.