Hi,
ever heared of winch launches up to 5200 ft (1590m)?
in the forum of www.segelflug.de I read the following. It might be of
interest for you
(short form translation):
During a glider acrobatic meeting in Fuerstenfeldbruck (Germany/Bavaria),
pilots from
Bavaria and Austria had the possibility to try a new launch method. Mostly
double
seaters were launched up to 5200 ft. (1590m). Acro pilots were enthusiastic
after 29
launches, because they could fly their full program out of the winch after
an only
90 seconds lasting start.
This was made possible by the winch manufacturer Tost (Assling, Germany).
They supplied a specially modified winch. Karl Hoeck from Friedberg/Germany
did the technical calculations and the design of the drum of the winch.
This drum had to withstand a pressure of 3 million lb (1400 metric tons)
from the 9842 ft
(3000m) of Dyneema rope with 0.18 inches diameter (4.5mm).
Organizing clubs were Bundeswehr Sportflieger Gemeinschaft Fürstenfeldbruck
e.V.
and Akademische Fluggruppe München. Munich control was involved.

With headwinds between aprox. 6 and 11 knots (10 - 20 km/h) following
altitudes have been reached:
ASK 21 and ASK 13 double seated: 5216 ft (1590m)
FOX double seated: 4594 ft (1400m)
Mue 28 single seated: 3937 ft (1200m)

regards
Walter