How thick are the cross frames? In my boat, many of the cross frames were only .80mm thick so I used the 3mm blocks to give more gluing surface. The lengthwise frames and some cross frames were 1.5mm so I added the 3mm blocks in high stress areas so not all got the blocks. Anything over 1.5mm only got blocks where there was a butt splice, regardless as to whether it was a skin panel or a frame butting up to another frame at a 90 degree angle. On your boat, I'd use the 6mm blocks

• at the joint between the sponson insides and boat bottom
• at the joint on the outside of the sponson insides and the sponson transoms
• in the joints where the lengthwise frames are glued to the transom at the rear of the boat. These would be in the under deck area.

I would use 3mm blocks:

• at the vertical joints between the lengthwise and cross frames not already called out, ESPECIALLY THE FRONT TWO IN THE SPONSONS
• at all glue joints between the sponson skins and the cross frames
• at the top of the nontrips, between the sponson transoms and rear transom. This is to give the deck more surface area to be glued down to as the other choice would be to glue the deck edge to nothing more than the top of the non trips which, if they are mounted at a true 45 degree angle, is less than 2.4mm.