got 35% carbon tint?

I originally posted this question on the Mods forum. Now that I'm getting around to acting on it, I might be having a problem with the vendor. First, the original message:

I recently had my rear windows tinted, and now I’m having a problem with headlight glare from cars behind me. It’s an odd sort of glare, more like 1†long horizontal streaks of light above and below the headlight, corresponding with the defroster lines in the back window. So if it’s dark out and there’s one car behind me with its headlights on, in my mirror I’ll see a series of several light-bars above and below each headlight. Very distracting with just one car, and almost impossible to see through in heavier traffic. I’ve also noticed I get more glare now off the tonneau cover and even the top of the 3rd-brakelight bar on sunny days.

I asked for 35% carbon tint, but don’t know what they actually installed as I was told it would take about 4 hours to install the tint and didn’t stick around to watch the process. I’ve washed the back window with non-ammonia cleaner as recommended by the tinter, but that didn’t help the glare. Has anybody else experienced this problem?

Yesterday I called the installer and he knew exactly what I'm talking about. BUT he's trying to tell me that this effect is a normal interplay between the defroster lines and the tint. When I told him that other Prius owners said they don't have this problem, he tried to imply that I might have some sort of extra-glare tint, or maybe the light is coming up through the smaller horizontal back window and creating the glare. So, to all you folks who have 35% carbon tint on the back window, and no after-market tint on the factory-tinted little back window -- do you have headlight glare on your back window?