Tweety -
We’re using a 0.5mm diameter x 4mm long arc, ~1300 lumens. Out largest issue is high-voltage leakage at 40kft operating envirnments. We solved it, but it took some interesting tweaks.
As for LED headlights… We are actually in the process of developing (have optics designed, and doing the prototype right now; for a LED based aircraft Landing Light… And if that’s do-able, then the LED headlights are a piece of cake in comparison. Just have to control the cut-offs a little better, but that’s all optics, not light generation.