I gues I am not specifically familar with the sanshin hubs but many cartrige bearing hubs (most I have worked on) dont have locating shoulders on the axel, the spacing adjustment is set from a pseudo-cone which lightly presses into ID of the sealed cartrige and a jamnut which are both located outboard of the cartridge. Even if the hub originally was made with a shouldered axel, it could be setup fine without one provided you have the pseudo-cone to fid the cartrige ID and the axel thread.