You will need to obtain some 16 ga material and make a patch panel. If it is just a few holes you can get away with placing some metal underneath and welding the hole up from the top and grinding smooth. A mig welder will be best for this. If you do not want to weld you can fiberglass underneath it and then put filler on top. You will need to clean the area under the cowl completely though to make the fiberglass hold. This is not an easy area to repair.