I've used it a LONG time ago. Shot it into the frame rails of a '66 MGB, allowed a few days of cure time then ramrodded the rails with fiberglass matt *loosely* to approximate a "honeycomb" effect. The resultant stiffening made a dramatic improvement in the handling of the car in auto-X. The interior was gutted and fire extinguishers were to hand as the 'glas cured: A great deal of heat and audible snapping occurred for the few hours it took for the stuff to cure. :shocked:
I wouldn't use it on exterior panels, tho.
When the poor dear was finally rotted beyond reasonable resurrection (after the 250K mile mark!) and was bein' cut apart with a torch, the plastic was still well bonded to the frame interior... the resulting FIRE is a story for another time. :wink: