why no vacuum adv with Solexes?

["Chris Robertson" <ckrobertson@hotmail.com>]

Why does the U20 with a solex setup use a distributor with no vacuum 
advance?  Is it because static timing is set to 20 degrees?  I would think 
that it could still benefit from more advance at high rpms.  Gordon?  
Amyone?

Thanks,
Chris
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