I haven't seen your version of it. I'm only answering because you asked, but I'm just making a half-educated judgement call.

If it's just a tiny drain hole in center of plug I'd get rid of the plug.
That thing has to drain, and the amount of drain water and the dirt are maybe both much more than what the designers expected.

Maybe put it back in for the "winter" when not using AC so that road salt and sand and other junk won't fly in. But only if you will remember to take it out again in the spring.
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DAMHIK: Don't Ask Me How I Know - - - Sven: '89 245, IPD sways, electric rad. fan conversion, e-codes, 28+ mpg - auto tranny. 500 mi/week commute. '89 245 #2 (wifemobile). '90 244 (spare, runs).