I use the starter sections for 2% grades as I have found it impossible to do a good transition otherwise. However, it is only about the width of say Atlas track so you would need to use two side by side with Fastrack. When I only needed to raise the track 1 1/2 to 2 inches, I use the starter up to a 2x4 laid on its side. The problem with using the the foam for long distances is there is nothing to attach the track to.
Good luck had happy railroading,
Don