I did mine at least 10 years ago and it still holds tight. My notes show a number of sealants that would work.

Loctite 5090 (002 989 73 20 10) recommended in manual
surfaces (002 989 47 20 10) recommended by steve brotherton
corners (001 989 61 20 10) recommended by steve brotherton

I believe I just used Loctite 5090, bought from Pelican Parts

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95 E320 Cabriolet, 159K