I, too, have worked fiberglass many times without repairing the gelcoat and got away with no read-out. Nine times out of ten, no problem. But when I worked at Eckler's, anything that got 'glassed got re-gelcoated. The boss didn't want that one-time-out-of-ten chance of read-out ruining the finish on a $40,000 custom Corvette (40K was a lot of money in 1981!). I'm glad all these folks have had remarkable luck with their 'glass work and we can argue about this all week, but if you've already had read-out problems once and you do everything the same way again, you will more than likely have them again in the same places. Albert Einstein once said,"Insanity is doing the same thing over and over again and expecting a different result!" When you finally get around to stripping and repainting your hood next winter, why not add that little bit of extra assurance by brushing on some gelcoat over the problem areas? An extra hour or two may save some further grief.