Reid,
I don't think the water thing gets mentioned because most of us have never had the problem. I drilled mine out to 1 3/4" with a hole saw (so I could put a button plug in there if I didn't like the results) and its been a lot of miles and a lot of rain and I haven't had any water get in there yet.
I'm not doubting you, but I think your prior post about this was the first I can remember seeing.
If I did have water getting in there, I think I would try gluing a piece of plastic pipe in the hole as a "standpipe" and fasten the foam/screen/whatever to the top of it.
