The boat is designed for electric power so it's not built as strong as a nitro boat would be.
The area you have in blue would be an internal bulkhead that would divide the engine bay from the rest of the hull, not a stringer. The boat does have a stringer that runs across the top that's only there so the deck has something to be glued to.
As for the red glue blocks, I would leave them since they are all that is supporting the edge of the bottom. If you remove them, the seam would have no support and would probably break after a few runs. As for the vertical ones, I would have gone with 3mm blocks instead of 6mm since the interlocking of the parts probably is strong enough to hold already.