The original T-33 kits featured a scale undercamber at the leading edge of the wing root that is part of the fuselage molding.
This cusp caused a delay in the stall of the wing root counteracting the wing washout. BVMs newer A.F.S. T-birds have had the tooling modified resulting in a much easier to land model. To modify an early version (non-A.F.S.) kit, follow these instructions.
NOTE: The F-80 does not require any modification.
Scuff the area with #80 grit sandpaper.
Fill the cusp with a polyester filler like Half-Time (auto paint supply store).
Grind L.E. up a bit to sharpen.
Finished part will have some positive camber as shown with ruler.
Patch prime and paint.