As for recommendations on added glue blocks, here you go:
1) I'd add 3mm(or larger) blocks on one side of the joint where the front two sponson framed are glued to the sponson insides
2) I'd add the same or, preferably, 6mm blocks along the bottom to sponson inside joint between the cross frames
3) I'd add 6mm blocks on both sides of the left sponson transom to outside of the sponson inside
4) I'd add a doubler on the inside of the right sponson transom and a glue block on the rear side
These are all areas that won't hold up without bracing. The sponson transoms take a beating when the boat is running so they could fail without added strengthening. The bottom to sponson inside joint is constantly being stressed by the water pulling and pushing on the sponsons. A butt joint here won't hold up before either pulling the wood loose or breaking it all together.
As far as the glue blocks go, I'd rip them diagonally into triangle stock. This will still give the same gluing area and strength but with half the weight