I do thank you for your replies.
When was just learning to fly CL, the rudder of the Flite Streak Trainer came off but it did not make one bit of a difference in line tension or flight characteritics. The rudder had the 3/8 in offset as called for in the plans. I made a new rudder, with no offset at all, and the plane responded just the same.
As for the Ringmaster, I did straighten the warp as much as I could by using the heat gun, and put just a bit of offset engine thrust by using very thin washers; I left the rudder untouched. The result was that the line tension is much better now, even though I note that at times the outboard wing tends to "hunt," especially in windy conditions. This was the same behavior that my Magician exhibited, too.
One thing I note is that the Ringmaster I have takes twice as long to take off compared to the Magician, but does track like it's on rails.
It was not a monumental warp-it was just a tiny bit...but as I am aware, in CL, a tiny bit can make a lot of difference.
Today I was practicing some wingovers to get a feel of the plane. When my instructor test flew it last week with the recommended elevator throws (about 15 to 20 degrees), it was barely enough to save the plane from diving into the ground in an inside loop. He increased the throw of the elevator and now the plane responds well, like the Magician. I have yet to loop it with the new changes.
The plane completes a lap in 5 seconds, and the RPM is about 11,000. By performing some calculations, I found out that the speed of the plane is about 50 mph.