The engine opening has been ruff cut and will be cut to the exact shape latter. The small area behind the nose ring is too complex to fill completely with balsa so I filled the area with a small amount of mirco-balloons mixed with epoxy. You can see the cuts in the triangle corners pieces to allow them to easily bend to the shape of the nose.

The inside of the nose area and fuel tank area was fuel proofed with epoxy thinned with alcohol. The bottom piece below the tank was fuel proofed before gluing it to the fuselage. I added a few triangles behind the firewall to strengthen the mounting.