Dear David,
the reason for the max pilot weight of 110 kg is rather simple: The (old)
European certification specifications for gliders, JAR22,
request, that the center of gravity stays within its limits at pilot weights
from 70 kg to 110 kg with parachute (!!) without
ballast, and that at least a pilot of 110 kg must be carried (see
JAR22.23-22.25). For a two seater, the value is 180 kg. So other
calculations, e.g. seat strength, belt fixpoints and so on are based on this
minimum value for the max. pilot weight of 110 kg, and
this 110 kg are printed in the glider specs. This has nothing to do with the
max. weight of 'not lifting parts' or with the payload.
So for pilots above 110 kg, it will not be easy to find a glider, which they
can fly legally.
Anyhow, you should contact the manufacturer of your glider. It might well be
he knows a solution.
Best regards
Walter