Depending on the material that you used, you could also just remove the abrupt change at the top... I'm thinging that if you were to use the foam "ramps," you could simply take a Surform to the joint and round it off. Harder materials might sand pretty well. The good thing is that you wouldn't have to remove all that much to get the shape you wanted. Like I suggested earlier, the IDEAL solution would be for the manufacturer to offer a transition piece at the begenning & end of each set. But then that would deprive us of the aggrivation wouldn't it??!?
dlm