Mine was factory glassed in the same location as yours, I finished what the factory started, by filling the gap top and bottom caused by the wood rub rail backer, that gave me a nice round inside corner at the shoebox. I ground 4" down the sides and 4" up onto the inside of the deck. then I did my layup of Mat and roving a couple of courses. then I mixed white gel into the resin and white washed to match the factory look.

Kalaazar,

I found this with the product number you posted;
http://usa.sika.com/en/solutions_pro...06sa01102.html

Looks like it is readily available here in the USA . .
From a quick read, this recommends the 292 for deck to hull . .

My paint guy looked at some touch up work today and he mentioned a 2 part high density putty that sounded interesting ( I'll get the name) but I question what the bonding surface would be applying to the inside. I guess if the wood strip were removed you might get an inch and a half or so on the top and bottom of the C cap joint if you put a thick amount of putty in... Glassing seems better to me but working in there would not be fun.

Grind a puddy knife to form the radius accross the rub rail shoe box joint, fill with short hair glass filler. (not some stay soft puddy that glass wont bond too...) then start with 4" wide strips of mat alt w/roving or bi/tri, up to 8" wide min and glass the deck to the hull from the inside - the right way.