Some odd reason.. Sig doesn't want to have upgrades such as this added to thier plans.
The Kadet Sr has been upgraded with ailerons and other neat stuff by modelers for 20 years... and they won't list how to put ailerons in the plans. (but the ARF will have ailerons...)
That's the only gripe I have about anything from Sig though... and all the upgrades seem to eventually get spread around.