That should be okay. The excess will squeeze out and hopefully won't be a problem.

I'm guessing that there's some movement of the horseshoe seal surface during thermal cycling, and that's why adding sealant to the bulk of the surface would make matters worse. When I did mine, I lubed the horseshoe seal surface with a light coating of silicone grease to ease assembly. I also practised with a couple of dry runs so I didn't have to fight time once sealant was applied.

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95 E320 Cabriolet, 169K