a few responses i've received directly:

==============
Don't know about the stemme in particular, but it is quite common for
flap positions to affect aileron travel. This happens in my ASW27. The
flaps and ailerons move together, so if the flaps are in
"down"
position, both ailerons are "down." Then the "up" aileron may not
be
able to move to its full upward position when the stick goes all the
way in one direction. For this reason in the ASW27, when you move the
flaps to landing position, the ailerons cease to follow along and
instead move up to zero degrees, in order to give full aileron
authority. I would not be surprised if the programmers of x plane did
not include this subtlety of the flap-aileron mixer system.

===============
I own an S10 VT and would like to know details about how to get it
into the x-plane simulator. Shall be a great way of practicing
while
at
home.
By the way, have a look at the Condor Flight Simulator. For soaring
training and competition, there is nothing similar.

===============
In real life, I use +10 degrees for landing. This gives adequate
aileron response for landing. I do not know the technical data for
the
mixing of the ailerons and flaps but they will reduce roll rate as you
increase the flap position toward LAND (+16 degrees). I sometimes use
full flaps for landing "short" with light wind or wind down the
runway.
My initial advice to a new Stemme pilot is to use +10 degrees flaps
for
landing.

===============
Yes you do have aileron control with full landing flaps. It will seem
to be a little restrictive and it does fly with a slower roll rate
with
full flaps but they do continue to control at a slower roll rate.