Boat covers tend to do a poor job of keeping the rear decks dry because they sag and rest on the wood trapping any moisture. Keith Hatton has found that stretching bungies from gunwale to gunwale over the boom keeps the cover off the decks.
I decided to try this but then wondered what to use as hooks over the gunwale. I thought some plastic tube with a slot cut out to slip over the gunwale might do and then I thought that a length of flexible tube might mean the bungies would not be needed; but what tube?
I asked Martin, my son, if he had any ideas and he came up trumps with 2m lengths of 22mm foam pipe insulation he found. This fitted over the gunwale easily and held the cover off the decks. I don't know how well it will work with extra weight on the cover from rain, or if the foam will tend to hold moisture but it is a very simple solution and it may do the job.
I am still looking out for some flexible 50 to 75mm diameter plastic pipe as I think it will probably be better.