I know that you can drill a hole in the ventilator ball of a Harbour Lights Lighthouse using a Dremel Tool with a small drill bit. The Dremel Tool must be mounted in a Dremel Drill Press. If you try with just the Dremel Tool by its self the tool will move and crack the ball. I have also install a small drill bit in a hand held fixture and drilled by hand. This is slow tedious work and there is always a chance of cracking the ventilator ball if you move the drill bit around too much.

With this being said, I would drill a small pilot hole with the smallest bit you have, then gradually increase the size of the bits until you have a hole large enough to fit your hanger in WITHOUT screwing it in. With the hanger in the hole (not screwed in or you may shatter the ball)apply some liquid/paste potting compound or epoxy in the hole to encompase the screwthreads of the hanger. This potting compund when dried will both hold the hanger in place plus give the ventilator ball support from within.

Good luck and let me know if it works!