You have to lightly sand the untouched/undamaged top sheet for the new resin to stick on top. So just mask past the smashed up edge so you will have new resin going on top. You will bring this raised repair line back down to the original topsheet height when you sand back. I laid tape over mind but this may be hard with your damage as it's over a wider area and you may upset the height level too low. What ever you can do to get this repair line flat to the topsheet and prevent sanding is good though. When you sand with wet 800 it cuts in fairly good. You don't need much time on the sander only a few seconds to blend it in between each grade. The 800 should bring it down to the right height while the 1200 and 2000 will polish the scratches out. The polish pad will then make all the scratches disappear completely.If you wouldn't mind giving me one more bit of advice. I'm a little conflicted on where to mask off the damage. I initially had the entire area masked off, just beyond where you see the top sheet begin to depress outward towards the edge. It's the white line like impression around that entire area. I basically laid down masking tape at that white line. So I'd be laying down epoxy over my original top sheet as well as the exposed fiberglass. Now I'm thinking not to mask off so far from the exposed fiberglass, and just mask off the two small areas around the exposed fiberglass and make the patch level with the impressed top sheet. What would you suggest is the best area to mask this off? Thanks so much.