I have to say, that is very ingenious, to use the left over plastic to make a filler/cement. Never would've thought of that.

I always just tack the two halves together with thin CA, then run a thin strip of 2oz glass/epoxy inside along the seam. Then I fill the whole inside with a layer of 0.75oz glass/epoxy to stiffen and strengthen up the whole thing. if the epoxy is used very sparingly, this method adds very little weight and the glass provides a little heat insulation from the engine that it otherwise would not have.

I then use just a smidgen of Bondo on the outside of the seam and sand perfectly smooth. Then, prime and paint. Seems to work pretty good for me.

Patriot