Just finished installing the swivel base. Clunked into place eventually onto the 8 bolts. On the rear right hand side of the swivel base the two swivel plates don't seem to sandwich the middle glide plate as well as the other sides too. Even when the hand turn bolts are turned right down there is still a gap of 1mm between the glide plate and the upper swivel plate. When not tight the gap is 2mm. Is this correct ? I thought there would need to be no gap to make this base secure and safe. I'm concerned in case my top plate may be warped slightly? I must point out I haven't fitted the actual seat yet as the base is being powder coated. Will the weight if the seat correct this anomaly?