Apart from the Quickie group of planes why aren't there more fast
biplanes? The quickies aren't exactly biplanes I know. It would
appear that 2 short wings can be built lighter than one long one since
the moment arm is half as long for the shorter wing pair. No struts
used because of drag, just short cantilever wings. You'd have a more
compact airplane that way with less weight that had the same drag as
an equal wing area monoplane.