Yep used it on a friends HSV and it made the light crack worse when he hit a stone. Its like a plastic which when placed over the light dry's hard like a proper perspect plastic.
We thought they were a good idea.
I have seen another product used by Kenworth Trucks Australia which is a just like your normal head light cover, but is attached to the glass of the light with a velcro type material. They stick on great and have worked for people i know, and considering they are on long haul trucks, they must be pretty tough.
The only question is, whether you can get them small enough, and if you are worreid about having a kenworth badge on the middle of your lights.
Otherwise i have one last idea. You can now buy cheap number plate covers, for 10 bucks. They are perspects, but very thin. IM thinking if you buy a set of them, cut them into nice neat circles, and then try the velcro trick maybe?
Otherwise im all out of suggestions. Except for EL XR headlight covers, you could buy them and put the velcro on them? Im not sure if they are big enough tho?
Its all worth a try, once one person works it out, the rest can follow.