The twisting is happening during your false casts so rubber legs aren't really going to help. They'll only stabilize it for maybe one false cast, then they'll provide extra momentum on all the subsequent casts and actually make the problem worse. The reason it's happening is that your flies are uneven. One of the feathers is probably bigger than the other or flares out more than the other. All you can do is make sure your flies are as uniform as possible. The hook also needs to come through the head so that it's perfectly even too.
One solution to your problem is to switch to a different fly. Yellow perch love fast moving white streamers.