folks,
I am beginning to fall on the heat side again. Where we park the vehicle is on the south side and there are several small windows. However we are in the woods so it would be a real fluke if that is what is causing this. The reason I am going back to look at this is the pattern of damage on the top. One of the responders pointed out that over the aluminum bows there is no damage. If you follow the heat theory as a focus spot traverses the top the bows would act as heat sinks preventing damage to the vinyl.
To try and prove this I am going to set up a time lapse camera to see if there is any focus spots. I may have to wait until spring since the sun angle is pretty low right now.
I will let all know the outcome and thanks for the input.
Bob