The rear end acts as a platform for the V-tail. I made a slight mod here. Building the Wings Wings are EPP and are nominally RG15 section. I say nominally, because the RG15 trailing edge is notoriously thin. But it's close enough.
Quality is good.
It all feels floppy at this stage but it'll stiffen up later when you apply the tape. The spar slots were slightly tapered instead of being parallel, so I opened them out using a scalpel and a custom sanding tool as described in the instructions. Tips with EPP Ease sharp bends by making shallow cuts with a razor saw on the inside of the curve. A razor saw is great for hacking large chunks from the fus. Coarse 180 grit wet and dry is best for sanding.