On the outside of the panel, V out the crack, then rip up some matt into shreads, brush on some resin, and work the fibers deep into the crack. If the cracks are severe, or chunks missing, then grind the inside of the panel with 36 grit and put a layer of matt on the inside. Before laying matt on the inside, use the method of shredded matt to fill the holes. After this has all dried on the inside of the panel, scuff it again with 36 grit and apply a layer of cloth that extends beyond the area you placed the matt on. For large repairs on 'glass bodies, I use core matt, or kevlar matt to add a bunch of strength to the repaired area... Might not be the way the reps say to fix it, but it works for me!!!!!