As an aside, I don't have the transparent roof either, but indeed my rear quarter windows are starting to yellow. Not a lot, but noticeable.
So, I already ordered some Meguiar's PlastX for my headlamps. I'll give the polycarb rear windows a go as well, and post the results.
I will look for some UV protection spray later and add that to the regular maintenance. Clean lamps are safe lamps!