The slots in the arm base work perfectly, you can just see one of the fixing screws which is not quite at the end of it's slot, this is the same distance as the cartridge from the end of the head shell slots. I can position the cartridge anywhere along the head shell and by using the adjustment in the arm base still align the stylus with the centre-line of the platter spindle. This feature allows experimentation with the effective length from the arm pivots to stylus tip.