Hi Nik,
Yes i agree with Andy my EW has been running with CB750 pistons for several years now and no problems . Well may be one , i fitted the pistons complete with oil rings and have recently had to replace the back cylinder EX valve guide ,i do use lead replacement in the fuel , next strip i may take the oil rings off and see if that stops the valve guide wear rate!!!! nice to have a clean exhaust though.
Regards
Clive