Moving the leadscrew will be needed in either case I think. I machined the leadscrew mounting brackets down to move it inwards. I'd suppose with the Ganderton method you would pack the same items with shim to move them outwards.
I'm very happy with the result of my conversion. The lathe performs as good as new now, without regrinding the bed. Well worth doing — by either method.
Not come across the "Ganderton system", but in a similar manner to Hopper I Loctited a strip of 1/16" x 1/2" gauge plate the full length of my Super 7 saddle shortly after I got the machine, as it was facing convex due to excessive wear on the short saddle guide face caused by poor gib strip adjustment.
After adding the strip, the lathe faced very slightly concave as it should & I have not had to make any further gib adjustments. There was sufficient free play in the apron mounting screw holes to align the half nuts without having to adjust the screw brackets on my machine. Adding the strip was a very easy fix to my saddle problem.
Nigel B.