You really do not need ailerons. With some extra throw in the rudder the Champ will do nice rolls, regular and reverse immelmans, snap rolls, spins and many other maneuvers that many folks think require ailerons. The only things it won't manage is stuff where a pure yaw with no roll is needed such as knife edge flying.
Even inverted flight will be possible. But you'll need to keep adding small bits of correction since with the dihedral upside down it'll be sort of like balancing a broom handle end up in your hand. But it is possible and doable without anything more than that little extra for effort and attention.
Heck, I've done all that except for the inverted flying with my rudder only model. That's right, no elevator, no ailerons, and no throttle control. Why this works is that the rudder induces yaw which works with the generous dihedral to produce a strong rolling effect. Basically forget that it's rudder controlled other than on the ground while taxiing and during the first portion of the takeoff. Once in the air just treat the rudder control as your primary rolling control. In other words put the rudder servo into the aileron output of the reciever and pretend that youve got ailerons. The model will do it's darndest to help you believe that this is the case.
To paraphrase the old spaghetti western Mexican outlaw "You don' neeed no steeeekeen' aileeerunz! ! ! !"
Kimber, nice addition putting that scan of the advert in. I've got one of the Early RC kits that I got from the original owner in trade for some old radio gear. They really are nice kits. I just need to stop putzing around with my other hobbies and get back to model building soon so I can put it together.