Looks like somebody had a tv set in there. You could do as you suggest, and use a larger piece of wood to cover up the problem area, or you could use fiberglass mat and resin to remake the area.
I would cut out the rest of the header and make a box or shelf to fill void.
I have actually seen where folks add a wire screen shelf above this ridge for additional storage and I have seen it done with oak shelf rail with little banister or spokes, it looked like it was OEM.
I think you are asking for a big mess by truing to repair with fiberglass. If you are not experienced with fiberglass, it is a real headache.
__________________ Ken Smillie
My 1994 36' Classic MH is for sale See it in the classifieds
I have zero fiberglass experience, but dont want to cut the header out as it will be nice storage for radio, dvd, etc. Plus I don't want to remove it for the sake of keeping it as whole as possible.
I think that if you had a wood trim piece that matches the current trim closely that you could "step" up the trim by adding a piece straight across the top of the storage unit, stopping or 'stepping" down where the end curves begin. It doesn't have to be very wide, just enough to cover the gap. Easy fix, and will look nice, like it had always been there, in my opinion. ~G
__________________ maxandgeorgia 1995 Airstream Classic Limited 30' ~ Gypsy Chev Silverado 2500HD Duramax/Allison, 4X4, Crew Cab WBCCI #5013 AIR #2908 WDCU Go, Mizzou...Tigers on the prowl!
I think John's suggestion makes a lot of sense. Try to glass it first, if it doesn't come out just right the first time it's called learning. The next time will be better. Remember you can shape it to some extent by grinding/sanding. Just make sure you use respiratory protection.
As has been stated, you can do something with wood if glassing it doesn't produce an acceptable result. Fiberglass will keep it most original.
How about drilling styrene dowels into the existing plastic for a strong mechanical connection, and then attaching styrene "mini-ribs" w/ adhesive to re-create the curve of the original piece. When that is done you can get busy with the fiberglass. It's messy, so practice on your corvette but it's very easy to do. When it hardens you just add more layers as need be. Once you have a good strong fiberglass shape you can add bondo and sand, sand sand. As far as the woodwork you can either redo all of it or patch it as required.