thanks very much for all your suggestions

in less than 24hrs you've given me lots of good ideas to think about, last night i moved the rudder slides forward and sealed the holes with a hot glue gun, (taped the inside and then pushed them in a little to ensure i get enough off a blob on both sides to prevent them being knocked out) looks like it should do the job for now

will start the search for something similar to minicell foam available locally and continue think about cutting hatches when it comes time to seal the hidden side of the bulkhead

eric e

buying hatches is tempting but here in the mountains there are no boat shops and even on the coast i wasn't even able to buy epoxy for the wooden canoe, had to make it from polyester, stuff can be bought overseas and flown in but it sounds more fun to DIY