If you absitively posilutely can't cut and sand one yourself it's a good way to go. One way to feather them out is to lay it on a flat smooth surface back down and feather with 60 grit sandpaper glued to a flexible backing about six or eight inches long. Take your time and check your work.
You could also enquire with a supplier like Kenny and see if he might do it for you. Advantage being that you could select other lengths, etc.
That kind of riser is perfect for a hill style. You can make it flat, reflexed or string follow just depends on how you design the form.