Hi Bruce
For my inside edges I always use a filler paste (P38). This sticks to the fibre glass a treat and can be sanded smooth and flush. No worries whether it will come unstuck. You might need two coats if it's unduly rough.
Hope this helps
ken
Yep, this is the way to go. I sand them inside so it is smooth-ish without unduely making them too thin. Then apply a very thin smear of car body filler and sand again. If it still isnt smooth, apply another thin smear and sand again.
Two points though. Dont add to much filler each time as you'll only end up sanding most of it off! Secondly, I dont make the surface baby bottom smooth and prefer a little uneveness in the finish as I personally think it makes for a more scalish appearance.