Check under your seat runners Potts. You may find tapered wooden battens on that year Trad. If there are, and you remove them you'll gain aroind half an inch. But note that a protruding bolt and nut will press into the floor without a spacer.and will make seat adjustment stiff.
Also the original Mog wheel from the factory was awful, but your local dealer is likely to have a few kicking around and it would make a good basis for butchery/experimentation.
