Hi Jez,
thanks for coming in.I already found an application with external hardware shift register.Would you suggest to check Mode 0 '51 ? I didn't look at that yet,because my '51 is so fast,has so little (actually)to do(every 300ms)and has plenty of Ram for my extensive hobbyist prog-style.
Is my assumption correct,that there is no timing problem? May be Steve M.T. can add some of his experience he got with these toys.
;-)