Wanting to mount headlight on my helmet and trying to decide between Zebralight H600 with 80 deg and 12 degree hot spot or H600F with frosty lens and 90 degree beam. Which would be better as supplemental light? I have handlebar-mounted light already.

How does the Zebra light work with a helmet?

If you want to wear a helmet then look at the Light & Motion Vis Pro. Beam pattern is outstanding.

Zip tie the mount to the helmet. I want a light that I can use in other instances and imo the Zebralight are one of the best out there in terms of output, runtime, versatility , and UI.

The Zebra is nice.

The L&M Vis Pro has a rear pulse light. They are very nice if you wanted something cycling specific.

But yeah, I can see why someone would want the Zebra. The specs are impressive.

Unfortunately I can't help with the H600 vs H600F question.

This light uses a rubber strap instead of plastic bracket. I tried it both on my
handlebars and helmet. No problems. Can operate with thick gloves; on/off,
lo/med/hi, slow/fast flash:

I've decided to go with the Zebralight H600w. Just figuring out if I will go with Mk III or Mk IV.

Get the IV, as well as the lumens/efficiency bump the UI is improved with different mode groups.

Yeah I think the improved UI is worth the $20 difference.