Tom,
Reg Harris used to have those canvas patches on his sprint wheels, I didn't know that they were applied separately, I always thought that they were part of the tire sidewalls - oh well, you live and learn.
By the way, when I raced track in England in the 60's all my tires were glued on with shellac, they wouldn't let you race with regular tubular cement. Getting a punture was heartbreaking, because the tire was so firmly attached to the rim the removal process of a shellaced tire was a really hard process.
Brian Booth
Toronto, Ontario, Canada