i did the bored tb myself, i have access to milling and turning machine.. i bore mine to 68mm cause anymore i would have hit the two hole at the side .. you would have to frabicate a new butterfly plate previous plate will be of no use .. the diameter of the plate was made to 68.5mm and you have to sand paper it to fit in your tb.. the butterfly plate is not round its actually oval. while you are at it might as well mill the center shaft like what rr did for their tb they claim better cfm .. there was a previous post on bored tb do search, very informative...... 
