Hi Bob, the dummy centre should be a snug fit in the shoe carrier C3 and a slip fit in the plate carrier C13. Assemble the carriers, shoes, links etc and hold C3 in a vice, keeping in mind that the bearing surface for the chainwheel bushes is not hardened and is easily marked, put a large screwdriver through the pins C14 and turn C13 in either direction against the plunger spring, I assume you've thrown away the double springs and fitted the single spring as it was found that the double springs binding during compression was a cause of clutch grab. The single springs are available from Derek Sayer although I should imagine that other people have made them by now. Turning C13 will expand the shoes to the point where the plunger hits thimble C12 and the linings should be 6 inches across at this point. I reline the shoes with oversize linings and jig grind them on the lathe to make sure that they're concentric. I hope this is of some use but please feel free to ask if you need more info. Cheers, Stu.