At 12:39 15 November 2013, GM wrote:
... The angle of attack of the glider during a winch launch is no
different than if the glider was in free flight at the same speed!

Actually, it is significantly different: the wing has to deal with the
tension in the cable (including the cable self-weight) as well as
supporting the weight of the glider. This could easily double the
AoA required in steady flight & smoth conditions towards the end of
a winch launch.