Let's use the C-130 for example. The %MAC (Center of gravity) doesn't change when you open or close the ramp. This is because the ramp is attached to the same point the entire time. The same applies with your wheels. If you're using a spacer, you're actually moving the connecting point (part of the stud that the wheel is sitting on) farther away from the car, which, obviously, leads to more stress. If you are using offset to move the wheel out farther, your connecting point remains the same.
Here's a picture with the ramp open so you understand what I'm talking about. The arms coming down beside the ramp are ADS arms (Aerial delivery system) They don't actually support the ramp, but are there to keep the ramp from dropping below horizontal in flight and causing the rear of the aircraft to lift...
