Good news, the fix came out better than expected.
What I experimented with yesterday was the ability to release the fibreglass and final finish quality when using packing tape over glass. The result was that the release was very easy and the surface area is glass smooth (except where there is an overlap of packing tape, which creates a minor impression in the finish).
I laid the cowl against the packing tape covered glass and used three layers of fibreglass (my cloth is much lighter than what was used to make the cowl) with the middle layer weave at 45 degrees. The result is amazing. Now, re-cut, it fits properly and ready for final cleaning of the lines prior to filler, sanding, etch primer and painting.
My end result may not be "perfection" as the original "out of the mold" shape was, but it is more than good enough for me.
Cheers,
Eran