Zenith 1 Carburetor leak trouble

[700rpm]

The drain plug on my Zenith will not stop leaking. I've tried everything I can think of and can't stop that leak, even with two gaskets on the plug. I'm reluctant to tighten the plug too much because it's brass and the threads on both the plug and the carb body are very prone to stripping. I've read every document I can find on these carbs and followed all the pointers for care and cleaning. Carefully checked to confirm where the leak originates. It's the plug. Some kind of gas proof sealant might do the trick. Can someone recommend something like that or another remedy?

Note: I am running Renners jets, all gaskets are new, and the float valve setting is spot on. I am at a loss for what else to try, and will welcome any suggestions.

Thanks.