It's called checking/crazing. Keeping it out of the sun is about the only to stop it from spreading further. There is no fix except to replace the siding. Your in the years of the siding that had a defect from the factory in the manufacturing process. Can't remember the name of the company but they are out of business now. Ours is doing it as well and if you look at coaches in the 03 to about 08 build you'll see they all have it on certain manufactured units. The darker colors is where it's most apparent. The surface attracts more heat in those areas and the cracking/crazing begins. I'm not saying to not wax your coach but it will not stop it. Painting is an option but if the shop that knows anything about this problem is honest with you they will tell you that it will return. Most shops suggest a repaint and to use brighter colors in the scheme where heat is a little less apparent. I had a quote from Newmar on ours and it was $28K for a reside and paint. That's not happening. Well good luck with yours and hope you can live with it as there is no real cure.
