jb weld is great. some people hate but it's really good.

-gotta use at right mixing consistency....don't let it get hard
-gotta get in the crack...covering just the top and bottom or outside isn't gonna hold. consider using additional support layers of thin plastic if it's not visible.
-gotta clamp it and leave it alone. longer the better.
-duct tape is your friend.

i've fixed tons of stuff...got tons more to fix.

 

here is my jbweld plus project of the moment.

front window finisher broke into a bunch of pieces. i glued and fiberglassed with slight redesign.

 

there's the fiberglass bit: