Pershing 1A Nose cone Part 1 for BT-80 tube size (2.6").
This is a two part cone assembly. See Part 2
here.
If you decide to go with an expansion foam,
seal the finish first as this is porous material. If you dont provide an inhibiter to force it to fill the cone, it will fail to expand effectively as the gases escape through the wall. I have done this with and without foam to a cone. It is plenty rigid enough without any foam application.