It's "home-made" but surprisingly worked flawlessly. I was concerned about the tension on the line needing a high torque servo to pull the pin but actually there is not much tension and it releases easily. The 4-40 rod connected to the servo goes through the aluminum tube. I bought a piece of thick walled tube from the local Ace Hardware. The 3/8 inch ply was cut out to form the brace for the tube, a space for the servo to mount and to look like a roll bar. I ran some fine cable to the wing tube as a support from the front. This was probably not needed and maybe "over engineered". Now that I have towed a glider I see that the glider breaks ground instantly and there is very little force on the release mechanism. I did nothing to beef up the structure of the Pawnee except to put an extra piece of ply on the turtle neck where pictured so I had more to attach a brace to.
For the glider, I bought a nose release and just epoxied it in. I added a wheel to the bottom of the glider thinking it would drag otherwise but it's on the ground such a short time it also is probably not needed.