A good way of picturing why bumps may feel more pronounced the further away from the centre of the aircraft you are is to imagine the aircraft as a see-saw. The pivot point and centre of gravity is roughly in the centre of the aircraft and this position is represented by the middle of the see-saw.
When the see-saw is rocked you can see that the ends trace paths through the air which are longer and more pronounced than any other part along the length of the see-saw. The closer to the middle, the less the movement and bang at the pivot point the movement is zero. Of course turbulence induces more than a simple regular up/down see-saw motion but the principle is the same.
Moment (or "turning effect") = force * distance from pivot...so a given force applied to the airframe by turbulent air will have more of a turning effect the greater the distance from the pivot.
V1R
