The proper matching of phono cartridge to pickup arm is really a matter of mass and compliance, not whether the cartridge is mono or stereo.
Best arm for a mono cartridge
Given that a mono cart has to move in one dimension and not two, is there an arm that you would recommend for this? I have a Phantom II with ZYX Airy 3 for my stereo but my Transrotor Fat Bob could take a second arm.