I have added rudder on one of the stabilizers of my FT Bronco. The effect in flight is not very big, but this is for sure due to the small size (depth 33mm) and the fact that I only did it on one side. I will rebuild the FT Bronco soon as it has now more than 250 flights and gets a bit soft. Especially the joint between the vertical stabilizers and the tail boom, but also at the connection to the hstab is getting weak now. But I think after 250 flights this is ok. For the new build I will go for a differential thrust solution.
In order to reinforce the vertical stabilizers of my current Bronco I had added BBQ skewers along the leading edge. Nevertheless I had to add more reinforcement after around 100 flights. I made 2 vertical score cuts on the inside of the vertical stabilizer and widened them to fit BBQ skewers. They go from the underside of the tail boom up to about 1/3 of the vstab.
It is maybe difficult to see, but the BBQ skewers are inserted where you can see the bulky lines
I just completed a flight, I added dual rudders similar to Bavarian Rc's setup. They work fairly well, you cant flat turn but they help with coordinating the turns. They really help in cross wind landings as the plane was torquing over when differential throttle was used, and now with just the rudders it's easy to glide in