I don't know if this will work for car and truck pyramids but for basic ramps the problem is simplicity.
In the game, all models are box shape, right? So, if a ramp is low on one end and high on the other, just raise the bottom end in binedit rather than lowering the top end. In game, tilt and the invisible part you hit is beneath the ground - viola, a ramp without the need of object boxes.
PS. In traxx 1.5 you can size and position object boxes using the keyboard for very precise placement.
Tip. Keys 1,2,3,4,5,6 and D/C, F/V, G/B, H/I
For an example of what can be done using keys, check out these tracks