Rework gasket on heat splitter box

The gasket in the heat-splitter box (Teknofibra) which replaced the original foam, as in

https://webuildplanes.com/adam-dickson-sling2/p/6553/replace-foam-in-heat-splitter

was removed completely and remade from JB-Weld high temp RTV. Gaskets were formed on both surfaces of the flap to achieve perfect sealing in both the fully open and closed positions.

The splitter box was reassembled and sealed as before.