T-bone collision damage to gunwhale

This past Sunday we had a crowded weather mark-rounding t-bone collision that resulted in some damage to one boat's rub rail and underlying fiberglas. The aluminum looks repairable with some straightening work. However, we're not sure where to start with the Fiberglas and gelcoat.  The horizontal indent is about a 1/2 inch, and there is a surface bulge both on the deck and the under-side of the gunwhale. The damaged area is just aft of the back end of the cockpit. Obviously, the gelcoat is chipped. Someone suggested just grind it down to shape, and fill with marinetex or thickened expoxy. Has anyone repaired this sort of impact before, and if so, how? 

Sometimes the extent of the damage isn't apparent by looking at the outside of the boat. Take a look at the area of impact from inside the boat. If there are any areas that look white, that means the fiberglass has been severely damaged from being flexed. Really, the best thing is to have someone who knows fiberglass to take a look.