Older Gulls come without a slot gasket. My Gull WAS a very wet boat in chop. An hour of sailing often required a good bale. Most of the water would come in from behind the board handle where it would ricochet off the back of the case and forward.
The solution, Velcro on the top of the case and on some rigid plastic to cover in front of the board handle and rubber at the rear.
This has transformed my Gull, 3 days away, two nights on board, 8 miles of open water and lumpy inshore, boat dry. Simple game changer.
The front section also secures the board down. I figure it would pop off if I ran aground but it’s not needed in more sheltered inland water. Both bits are stored Velcro-ed to the side of the case.
tinkboats 
Nicely done, I’ll copy that if you don’t mind. Ditto the matting. In the wooden Gull I restored to use as a rig test-bed I didn’t bother with the thin floor slats (previously glued & clenched), but using that tyoe of heavy mat will spread any load which might otherwise be problematic.
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Hi Pete
Enjoy your testing
I had tried all sorts of schemes pushing stuff into the slot but this worked well. The matting prevents anchor bounce.
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