RE: Byron P-51
Many moons ago I had this same kit. The fuselage should come with a foam "former". It goes into the back half of the fuselage 1/2 way and then the other half goes into the front of the fuselage. Then once everything is joined it becomes more stable. That is the only former in the back part of the fuselage. I am pretty sure I have the instruction manual for mine still. Give me a call if you want me to look for it. 256-736-3852.
Greg