Canexel Siding On Dormers?

I am installing CAnexel Siding. It is a fibrebased material with a weather proof exterior. The back of it is fibrous and not protected. Here is my problem. I am siding my dormers and the siding will have to be cut to conformer to the slope of my roof. First..would I have to seal the cut ends of the siding? And if so..with what? How high should the siding be above the surface of the sloping roof (meatl roof) Should I caulk between the roof and the bottom of the siding to prevent ice daming in the winter or will that trap moisture that gets behind siding. I was also thiong about caulikng between roof and bottom edge of sidng..but leaving small gap at the lowest point of the siding behind the outside corner trim to allow melting water to escape. Has anyone worked with this stuff?