i cant seem to find one where it was fully finished but here you go. you need to ream it deep enough so that the rubber is almost touching the hub. i did the first one by hand. even though i through drilled it before i started, it still took about 30 mins. the second one i couldn't be arsed with so clamped the buggar on the cross slide vice and done it on the lathe, still took a while but didnt kill my hand and the result was much better.
if anyone wants i can sell you a made to order, modified axminster reamer that will fit in a 13mm chuck. £12 including postage.