Following comments about bracelets in general and the Speedbird III in particular being difficult to get exactly the right fit, I looked around for another clasp and received a sample this week.
It appears to be a strong clasp and has up to half an inch of adjustment in 4 ratchet clicks. I propose fitting this to most bracelets.
http://www.tz-uk.com/pics/newclasp1.jpg
http://www.tz-uk.com/pics/newclasp2.jpg
http://www.tz-uk.com/pics/newclasp3.jpg
Eddie