Hey Sean, good eye for structure. Any serious flex in that area could lead to fin or stab flutter that would surely ruin my day.

The stab is one piece with c/f reinforcement. It slides into/through a cutout in the lower portion of the fin. That portion of the fin is fully boxed - plywood ribs on top, c/f reinforced fin spars with shear web at the front, and 3/16" thick balsa ply on the sides with glass inside and out. The stab will be epoxied in place with supplemental glass as needed. The fin spars penetrate the fuselage shell and will be epoxied from the inside. It is very rigid.