Morris 9 series meter rollers

New to us 9365 VRT tank, it’s an 8 run, was previously feeding 7 outlet secondary heads we have 9 outlet heads so according to the book we need the wider meter wheels , we dont use heavy rates , 50kg ha seed and up to 110kg ha fert,not sure what that is in inches, can we just calibrate it as is and the shaft spins a bit faster to make up the difference or get the wider meters? Cheers