Garibaldi,
Doug has has given an excellent summary. The only point I would make is that your arm should have 17.31mm overhang not 14mm.
Peter,
It is interesting that few of the current arms with the facility to rotate and slide the cartridge choose to do as you suggest. It seems an obvious design advantage, particularly if the two movements are kept separate. It is, of course, simpler and cheaper to combine the two functions on a bar between the cartridge mounting holes.
John
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