How about a biplane configuration wherein the upper and lower wings
are conected only at the tips by an endplate? Within a limited span you
could reduce the chord of the wings for a given wing area and the
endplate would help with the tip vorticies in the same way as a winglet
on a monoplane glider.

BUT; Absolute hell to trailer and rig and I'm sure that if it would
work one of the Akafliegs would have tried it by now...

Anyone ever tried to soar an autogyro?

And, yes, I have gone crazy waiting for the flying season to start
again.