I bought the wheels (built) from Just Riding Along, who were excellent. They have an article on converting them to tubeless for both road and cyclocross:
http://www.justridingalong.com/news/2011/10/converting-velocity-a23-rims-to-tubeless/
Also, there seems to be some positive experiences here:
http://cowbell.cxmagazine.com/forum/topics/velocity-a23-tubeless
@Soul started
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I bought the wheels (built) from Just Riding Along, who were excellent. They have an article on converting them to tubeless for both road and cyclocross:
http://www.justridingalong.com/news/2011/10/converting-velocity-a23-rims-to-tubeless/
Also, there seems to be some positive experiences here:
http://cowbell.cxmagazine.com/forum/topics/velocity-a23-tubeless