It's hard to imagine that it wouldn't A black cloth ought to do the trick.
I assume that the HUD reflections are visible whether the HUD is on or off? Looking at the photo
@hydbob posted, I can see from the shadows that the Sun is pretty high in the sky, but not directly overhead. Maybe 10:30 am or 1:30 pm. I'm curious how wide a range of Sun positions causes the HUD to become reflective.
As I have a GGT order with HUD, and I'm impatient to get a Gravity, the talk of reflections is making me wonder whether I should amend my order to be without HUD, and hopefully get delivery when they start making white Gravities. If I could get the GGT with HUD today, the reflection probably wouldn't put me off of keeping that in the order, but I'm feeling jealous of those of you with a Gravity in your driveway.