From Bob Graham, via Musical surroundsings:
Looks like an arc protractor is in order. There is still a wee bit of play with the headshell in the jig. Enough, imo that even with a 9" arm, you could be off slightly zenith angle wise.YMMV
I checked with Bob Graham and while you are correct that the alignment jig is for the 9" arm, there is actually only a 1/2" difference in the effective length of the 9" vs the 10". Mr. Graham recommends moving the cartridge back in the headshell about .05" from what the gauge shows to achieve the proper overhang.
Effective Length: 10" = 248mm
Spindle to pivot distance: 10" = 229.4mm
Looks like an arc protractor is in order. There is still a wee bit of play with the headshell in the jig. Enough, imo that even with a 9" arm, you could be off slightly zenith angle wise.YMMV