Hi Steve, to increase the area of the vertical fin the model 1 - 2 - 3 and very first 4's had a short rudder fin the later model 4 had about a 9" taller tail assy so this is a way to increase area without cutting and welding others have done this and I'm hoping it will improve the flt char. abit if not it will be easy to remove.
I had a Gredes park valve so I used it but Matco makes one that I would have used had I not had this one. The biggest thing with using the Gredes valve figuring out how to go from AN fittings to the Nylo fitings that I have in the plane, mounted the valve between the rudder pedals on the firewall installed a push / pull cable and connect the hyd lines and bled the brakes. Yes there has been more than a few time I wished I had a park brake. The Matco valve has nylo type fittings on the valve assy.
If you look at picture 3 you can see the valve between the pedals the push / pull cable is mounted at the center lower pedestal just above and left of the cabin heat control knob.