I had a similar situation when fitting mine. I inserted a couple of washers to fill the gap. Before tightening up I flexed the suspension to get everything to settle in. I preferred this to leaving all flex to the poly inserts. In my mind this set it to a "neutral" position with my weight only in the car.
Kitcar suppliers advise a similar method when building suspensions to let the natural weight to preload/pre position the parts to prevent out of line stress on bushes in particular.
