Good question, I have a Vegas with stress cracks. Have the same idea. Sand it down then fill with expoy.
I used to bild custom corvettes. We would V out the cracks then fill them with resin mixed with very fine cut up mat.
Rick you forgot one thing! We was tought this in trade/vocational school and semmenars.. With fiberglass repair on VETTS.. when fixing stress cracks.. first you need to drill holes at the end of each stress cracks..you can use 1/8 and smaller drill bits.. by doing that you stop it from spreading any ferther/stop the cracks dead in there tracks..then grind a V bevel in the cracks..then you grind or sand the rest of ther area with 80 grit sand paper ,then like rick said use chop up glass cloth and resin.. then apply that into the cracks.. or you can use VETT BOND.. THAT STUFF IS THE BOOM!!!THINK THAT MADE BY SEM.. that mixes like bondo..THATS WHAT WE USED TO BOND FIBERGLASS PART TOGETHER..IF THERE ANY IMPERFECTIONS..THEN GET ICING MADE BY SEM.. MIXES LIKE BONDO BUT IT SPREADS LIKE CAKE ICING AND SANDS SUPER EASY... YOU CAN SAND THAT WITH 180 GRIT SAND PAPER WITHOUT CLOGGING THE SAND PAPER...ITS FOR AUTO&MARINE USE =water proof..Then prime it ..then sand to paint with 400 grit wet sand paper,then your good to go..
Your right Missy, I forgot about drilling holes.(****, another seniior moment) As far as Vett Bond and that other stuff, We didn't have that stuff back when I fixed cars. We used lead, Bondo and spot putty. Hell, the only filter we had when painting was the cigarette in our mouth. Now they use Moon Suits.