Just pulled my strut out of the boat. Had bent it and the shaft lastt season. I do not have the moat around mine though it sits in a pocket similar to yours. The boat is solid glass in the area of the strut. My opinion is you should be fine just filling in with some 403 and then fairing with 407 or 410
For reference, on the inside of the boat, the two front strut bolts are on the cabin side of a bulkhead that runs almost dead center across the strut. You have to access the two back bolts from the cockpit.
The four bolts are each backed by a pan washer. When I looked at that I decided to beef it up. In the engine compartment, I built a 5/8" thick dam wider and longer than the strut and filled it with a 403 mixture. Then I put a1/4" ss plate across the top of that. My two front strut bolts run thru that ( probably an over kill)
