Body filler in the trunk?

Thanks for the input fellas. I looked and I actually have the USC All Metal and not the Evercoat brand. I shined a light from the bottom and don't see any pin holes but I'm sure there's some there that I can't find so the seam sealer from the bottom is a good idea. Good tip on sanding the all metal before it gets too hard. This thing is already enough work, the last thing I need is to make extra for myself. Thanks again.