Technics SL12xx & 12" Arms.
It can be done!
Richard of Vantage Audio has emailed me to say they manufacture a sub-base specifically to allow the fitting of a 12" arm to the SL-12XX series of turntables. So there you go! :)
Vantage Audio
My own Denon DP-3000 is with Vantage at the moment having a service and some modifications to the power supply. Richard seems very nice guy to talk to and is a goldmine of knowledge and experience when it comes to turntables, have a browse around the website, in particular the 'gallery' where you can see some impressive repairs to some very desirable decks!
Cheers...