I think your asking for trouble (Cracking or worst yet it punching through from atop pressure). IMO you need to reinforce the backing ...I filled mine with small squares and 4 tig welds on each square. Bondo-ed it and smoothed it and done. Of course I gutted some sheet metal out my wing to get to it, but it worked fine. I have heard of guys just goind over it with bondo... but I wanted security. That is just what I did, but good luck.