Reinforce the bar from the back with additional layers of Glass. Always best to reinforce the bar, may even be worth adding a bit all the way along the inside ogf the bar. Do you have pics of the Damage, inside and out? Clean out any loose fibers etc on the outside and put down small layer of Fiberglass, sand and fill with filler and finish. You can use fiberglass filler to fill the joint / hollow after you reinforce the bar with glass but you will need power tools to sand it, it is as tough as nails, I use sanding disks on a variable speed angle sander, also orbital and palm sander starting with 60 grit and working down to 120 grit. I use nothing finer on bare Glass filler or Fiberglass. I then filler with std filler and sand as per normal. If you use Glass Filler you will need to treat it just like fiberglass when sanding and get ready to itch
