After some back and forth discussion, it seems pylon-mounted wings could have a lot of potential for sailplanes.
WRT aerodynamics, they make a laminar upper wing and much more extensive laminar flow on the fuselage possible.
Structurally, notably yaw forces might be problematic (ground-loop), but nothing impossibly difficult. With the possibility of a mid-wing one can remove the heavy spar stubs and control connections and also reduce complexity a lot, notably for drag brakes and flaps.

A few designs from the past come to mind. SH had a pylon-wing on an experimental Cirrus and it reportedly flew well. The Streifeneder Albatross and the Akaflieg München Mü31 are heading in that direction, but are only halfway to the advantages of a full pylon wing.

So why don't we see pylon-mounted wings on modern sailplanes? I can see why not in production ships from the established factories; any radical change demands a steep and risky learning curve. But for new factories and/or experimental ships, at first glance there seems a lot of potential.

Any major issues with pylon wings that we've overlooked?