I have the opportunity to mount several and different compliance/weight cartridges, between them: Ortofon 7500 ( 11grs and 13cu. ), Koetsu RSP ( 14grs and 10cu ), XV-1s ( 13grs and 12cu ), Accuphase ( 8 grs and 12cu ), Ikeda REX9 ( 16grs and 4cu ), Ortofon MC2000 ( 10 grs and 18-20cu ). No one of these cartridges and other ones that I try with the 506-30 performs bad, some of them are not the best match ( effective mass/compliane ) but performs good.
These SAEC double-knife bearing design are really good and its ceramic build headshell help in good way to permit that different cartridges can/could run ok.
I don't know with which cartridges do you want to try it but the best answer is what you will hear with those cartridges.
About VTF there is no precise limit, this depends on the headshell/cartridge weight ( the headshell is 18grs. ) and how much you have to carry the counterweight to the pivot for balance it and from there how much space leave forward to the counterweight. Of course that you can try it with different headshell weight to change ( lower ) its effective mass trying to get a better cartridge match. Very good tonearm indeed.
Regards and enjoy the music.
Raul.