H201 Libelle and wing dropping

Since 3 month I am proud owner of a H201B with 17m wingspan and
"Speizklappen". The glider I owned for 4 years, before i bought the
Libelle was a Astir CS77. I like the handling of the Libelle very
much, the only point I really have problems with, is that the Libelle
loves to drop a wing at the beginning of aero tow. Every take off that
a friend or me made with the glider was close to a aborted take-off.
Other Libelle Pilots said, I should try to open the air breaks for the
first 100m, but none of them owns a 17m version, which has extra
weight on the outer side of the wing because of the wingtip extension.

I am not used to this wing dropping by the ASTIR so I hope I can get
some additionell advice here.