Warren I agree about the sun eating the plastic in the South. I could rub my thumb across the luggage rack behind the seat and leave a mark. I think if I tried I could plow a furrow with a fingernail.
The sun is a powerful thing. If you don't believe it spend a full day on a Florida beach and leave the sunscreen at home. Ouch.
Brad
This was my experience as well. I used the NT to commute whenever I could and a couple summers were really hot and dry. I always parked the bike so the sidestand faced north. You could see a dramatic difference between the right and left cowl. The right cowl recieved the full treatment from the sun and was getting brittle. The left cowl was black and didn't easily scratch. I was mainly trying to protect it from further UV damage when I tried the plasti-dip. I felt the plasti-dip was a good option, but using a krylon paint for plastic would be a good option too.