Over- kill?
As you can see I don't plan on having my cockpit flex. It may be over-kill or very good? I have to add some triangles to the rear and I should be able to fillet the sections 124-169. They're only 2" (50mm) cut of ply, so bugger all weight but should add a lot of strength.
While I was pondering (and asking) how to fix the cabin sole down I thought I would canabalize my spare Flying Fifteen spinnaker pole. It seems to like it new role in life as a compression strut in the cabin of the i550.
Oh, and while I was there I thought I would fit some solid meranti 1'3/4 X 3/4" (42x19mm) to the sheer line. I had pre-cut my frames before they were fitted in the hull, so all I had to do was slot them in. I did use a number of screws to hold them in place while I was bending them into position and while the epoxy set.