Got some foam from wally world for a dollar and some change. Took it to the band saw and made some foam plugs to seal up the vents in the helmet. Should have done this a long time ago. Seems like it should work at keeping the cold wind out and maybe some warmth in. I think it turned out well.

Good stuff! Helmet looks like a bowling ball. :D

Assuming you've got room inside, a great way to keep the noggin warm is with one of these:

Noggin warmer

Duct tape works about the same, with much less work.

If you plan to be out in the cold for extended periods, a ski helmet is a very good investment.

Duct tape will be a wind block, but won't stop heat loss through the vacuous air channels. You've done the warmest option adaptation. Room or adjustment(different/partially removable padding layers) to wear a winter wool/fleece hat underneath in winter is important.