Bending curved track vertically does sound like an interesting challenge. I've done transitions to grades up to 12% with O tubular straights, and to grades up to 8% with Gargraves Flex (vertical bend while straight, then formed the curve). I always use plywood jigs for these bends, bending the face of the plywood for the vertical track bending, and cutting the edge of the plywood to the inside diameter for the regular curve bending.
You're looking at much lower grade changes, but with rigid plastic base/roadbed. I guess I'd build a heated jig for the vertical curve out of 1/2" plywood over an oil-filled space heater, then use a heat gun to warm the plastic a little more while pressing the track down into the jig, to form the bend. Has anyone done this with their plastic track?
