Thanks much for the input guys, you're all great!

I would absolutely think there was a metal core in the center, but when I drilled and tapped the screw to repair the bottom spoke, I only got plastic shavings, and I drilled in about an inch deep.

The button will work, but in a pinch the stock horn button would be better! I might re examine this issue later. Next big items are sealing the windshield halves and install the heater control valve and cable.