Jo No. 5 mounting problem

  I bought an EAT Jo No.5 and have been unable to mount it on my SME IV.5.  There is an inclined stiffening ridge on the underside of the headshell that prevents me from lining up the mounting holes.  Yet Ken Kessler, when reviewing the cartridge, mounted it on an SME V without mentioning any difficulty.  Has anyone here tried using a A Jo No.5 on an SME arm?