Good question - what line are you spraying, and what sealer options do you have on the shelf? The answer changes a bit depending on the basecoat, so I'd consider that first. That said, here's my general take: I run urethane sealer under urethane basecoat, pretty much every time. The chemistry matches, it cross-links fast, and it lays down flat meaning there's no grit from the epoxy telegraphing up through your color. The real problem with epoxy as a final sealer isn't adhesion, it's the recoat window. Epoxy stays chemically active for days. Nib sand your base, cut through to that epoxy, and try to spot in and now you're fighting swelling, edge mapping, and fry-ups. And your burn-throughs don't need epoxy to be safe. Hit those bare spots with a Bonderite wipe or an etch pen first. Clean metal, keep it wet a full minute, let it dry, then get your sealer on within 15 minutes. The zirconium conversion coating is doing more for corrosion protection than the epoxy might have been anyway. On the DTM argument I think most of the pushback is really about guys spraying urethane straight over untreated bare metal. Treat the metal first and that debate changes. Hope this helps!