Soooo I was home the other day during the middle of the day... and "The History of the Bra" was on television....
There actually was a very interesting segment on sports bras - someone did a motion study to determine what the best design for a sports bra for more well endowed ladies would be. They tested - stretchy material, individual cups; stretchy material shelf style; stretchy material, shelf style doubled up; and stiff material, individual cups.

The non-stretch material won hands down, for comfort for the tester and in the computerized motion analysis. The doubled up traditonal shelf style sports bra did cut the bounce, but the tester felt too constricted by it.