If you generally follow the diagram it ends up on the straight taper of the tail boom which is pretty long and non critical.
Measure the length of your level, multiply by .052, and make a spacer that dimension.
QED
UH

Ok, thats sounds simple enough. I've never actually performed a W/B with an incidence board, but thought that the location would be more critical than you mentioned due to it seems fuselage booms taper slight at first and increases towards tail. Just a general observance though and never really measured or compared.

Thanks.