The 64fx is good as it is, in its stock condition.
I use Stevenson geometry with my FR-64fx + FR-7fz cartridge, as recommended by the manufacturer (Ikeda San). With this cartridge you can not change the geometry as you simply can’t twist the cartridge in the "headshell". With conventionel cartridge you can change the geometry, but not with a headshell integrated FR-7 series.