The Bump effect in your G-Belt output mixer contains vertical G-forces. You will want to increase the slider for the Bump effect to feel more elevation changes in the G-Belt.
That said, how your brain perceives this will depend upon your physical mounting location of the G-Belt. Mounted on a GS-5, the harness will pull back and a little down on the shoulder, giving the brain the chance to align with both the bump portion and braking portion of the forces. Your upper torso height relative to the harness holes in the seat will determine how much you feel of a pull backward vs a pull down. Interestingly though, the brain adapts quickly and pairs the harness movement with other sensory data. Even if the harness pulls back on you as if you are braking, your brain will apply context and you will perceive a bump or vertical force.
Thanks