Rust coming through new epoxy - help

[ItWillBeSlow]

Primed the inside of the repaired cab metal and put part of the removed B-pillar lip back in. I put more in than I show in the photo, but it is not exactly as removed.

I welded it back up from the outside as well. This is another area unfortunately where you will not be able to prep or paint your welds from the inside. I sprayed some eastwood sealer in the crevice from the backside, and will also probably fill this area with seam sealer when I am closer to paint.