If I remember correctly, the Senior has a nose wheel. Changing to tail wheel will change the CG, maybe make the plane too tail heavy. It also changes the angle of attack of the main wing while taking off and landing. That can cause other problems for landing and take offs because it might float from the extra lift before it is going fast enough to actually fly. The final concern I can think of, is the structure strong enough to handle the loads of the tail wheel. In order to make it work you may have to move the wing position backwards and move the main landing gear forward. Nose wheels are generally considered easier to learn on, changing to tail wheel will not be worth the trouble if you are just learning to fly. If you are new to this hobby, I would highly suggest NOT trying to add ailerons and tailwheel until after you are able to fly the plane the way it was originally designed. These changes are fairly complicated, but they can be done. If you do not have the experience to do them correctly, you are more likely to only cause yourself more headaches.