thanks for the tip Ian, not thought of that one.......have some scribes somewhere........will try on the other parts, but this morning i hadn't seen your input, and finished the trimming with a knife.........not ignoring that info though.
This morning I trimmed off the 1.2 millimetre of plastic rim left on the hull of the rib with a sharp scalpal blade in a craft knife, and then sanded the edge smooth with 60 grade abrasive paper.
Now this is where I deviate from the instructions in the kit. instead of cutting out the round bulkhead supports that go inside the two halves of the sponsons and then gluing the sponson halves together before gluing the assembly on to the hull, I have glued the bottom half of the sponson to the hull first......
WHY , Might you ask!?
Well, when I built my first kit of these models I did as the instructions stated.........after doing so, and ending up with a nice strong construction, I went to glue it the the hull, and in the curing process that I had not checked the night before, the two halves had twisted overnight by about 3 mm out of scue, which wasn't noticed until trying to glue to the hull, and the boat ended up twisted permanently.
And so on the next model that I built, and in fact when I designed 3 years ago a D Class vac formed rib that I sold to Mountfleet models in 2022, I did the same, gluing the bottom half of the sponson to the hull first.............never had a problem with twisting since.