mang...that plastex stuff looks dope!
abs glue is very pliable but strengthwise if it's somewhere that would flex a lot i wouldn't use it.
no it won't stick well with fiberglass but OG plastic pretty good.

 

i can't remember where i saw it, but there was some other stuff that wasn't a two part epoxy (resin/liquid), but it was a paint on fiberclass looking liquid that patched up the hard plastic areas. looked pretty cool as well, i'll see if i can track down a link.

 

Seems that one would need a chemical lab suitable for making WMD's to do a proper repair job on a bike.