Only the glider pilot can control that. Might as well tow sport planes with no engines if you change the airfoil. I have about 10 hours in full scale sailplanes and my very first takeoff leaped into the air. Scared the cr@p out of me. Even thought they told me it would happen, you never really expect it like that. The instructor just laughed and said he had it. I quit cause I just couldnt afford it anymore. Like Minnflyer says, speed on the glider creates a lot of lift.

Yep! CG has been what kept mine rolled up on the back burner. Not very much info on these plans.
Edwin