OK, here's that final tip on strengthening butt-joint panels. This trick I learned from the late Tony Delvecchio, president of the LIARS club until his passing. He was an incredible customizer that had an eye for what would work, and what wouldn't. This is how he held some of them together.
Materials needed are 3/4 ounce fiberglass mat from the R/C dept. of a well stocked hobby store. A straight edge, a hard surface to cut on, scissors, toothpicks or a small steel paddle, Xacto w/ a fresh blade, and gap filling super glue.
Cut it to a smaller size on a hard surface. The closer to the final size the better. If you trim it with scissors it will shred a bit and get sloppy.
Once it's laid over the area that needs to be reinforced, you soak it with super glue.
Smooth it out and work the glue into the matting. It will soak up the glue on it's own. Just push it down tight against the surface your strengthening. When it dries it is very stiff. It can be cut and sanded after it cures, but trimming now makes your life easier later.
Now you have a fiberglass reinforced patch overlapping the two pieces. A piece of plastic was used also, but due to the shape the matting conforms better, creating a stronger patch. Plus it's very thin and won't interfere with other components. This works for top chops, frame sectioning, altering wheelbases. Anywhere you need to add strength to an assemble that may flex and crack.
Great tip Tony. Thank you.