Nice job you're doing there chap! I am in the same situation. Boat officer/caretaker/Instructor for our dive club. Trying to keep the boat in good condition all the time & not let people add their own little add-ons/repairs etc?
Not as clever as you though, I tend to get it professionally looked at if I think the repair is beyond my capabilities.
We installed aluminium plate to cover the top of transom preventing excess splashing while 6 divers are kitting up, also 2 auto bilge pumps help massively! Dry boat now, instead of always standing in a puddle!! lol. Look forward to seeing more pictures! Thanks!