I have seen an SME V mounted on the obsidian plinth.
Here is an example of an SME IV ...
http://www.theanalogdept.com/k_mccarty1.htm
All he needs to do is make a template. Trace the SME mounting base, outline and hole, onto a piece of cardboard, cut the base out and measure the pivot to spindle of 215.35mm. Then just move the cardboard around on the arm board until it fits and the pivot to spindle is correct and mark up the board for cutting - pretty straightforward really.
Here is an example of an SME IV ...
http://www.theanalogdept.com/k_mccarty1.htm
All he needs to do is make a template. Trace the SME mounting base, outline and hole, onto a piece of cardboard, cut the base out and measure the pivot to spindle of 215.35mm. Then just move the cardboard around on the arm board until it fits and the pivot to spindle is correct and mark up the board for cutting - pretty straightforward really.