If I remember right Horizon had a set up to carry a glider a few years ago. You might give them a call and see if it's still around. A friend and I built a set up for this but it's been awhile and I don't remember to much about it and can't find the pictures.
I do know that we had a ball with it and it worked great, in fact we used it for a couple airshows. In respect to turning: we found that while the glider was on board that once in the air it was better for the glider pilot to do the steering.
Sorry I can't be more help. You might want to go to the glider forum, they should be able to help you.
ENJOY !!! RED