Fiddly to set up for sure. A good deal of calculation required vis a vis the ballistic curve and point of aim, centre to centre distance of bore and scope etc.. One way to do it would be to attach the rear base to the rear "leg" so that the two mate properly and then use the front base and scope to locate the rear base; all while getting the proper vertical and horizontal alignment! Not easy to do of course as the rear base only goes as far down as the metal removed from the backsight "ear" permits! I've just set up bases on a Ross Mk.III and it is not a simple process if proper collimation and range of adjustment on the scope is to be achieved.