Okay so here is what I have so far. This week has been hectic so haven't really gotten to work a lot on the plane. I can't get the correct size dowel so that idea is out for me.

The picture shows what I have done so far.

I epoxied the 4 sides of the firewall (NOT shown on drawing) - fixing the firewall back into it's position.
Then also epoxied the gaps/joints (as shown on drawing)
I'm going to glue the triangle stock as shown aswell.
The piece of plywood was installed after the previous crash which took out all the supports in the nose - the tank rests on this.

The drawing may not be 100% correct but it's an idea of whats going on inside.

Should this be sufficient?