I have now measured my clutch plates and would be grateful if you could confirm or deny they are the same type / dimensions as you bought from Barnet.
My clutch plates are 5 15/16" OD.
There are 12 locating tabs on each which are 0.54" wide and 1.0" apart.
The friction part of the plates are 0.44" wide / deep
A picture paints a thousand words, so here's some pics: