Goodday nightflyer01,
I have read your question about retractabel landing gear for a 337 Cessna. I am also building a 337, and also wanted a retractabel landing gear.
In Switserland a guy is also trying to build this gear with piano stings and a winch, but it doesn't lookes solid enough.
The problem that you will have to face, is that the rotation of the main landing gear is greater than 180 degrees, and a standaard servo or pneumatic cilinder won't do the job.
Mechanical I have build up de rotation of the main landing, from the parts out of the box, and it works. Now I'm building the pneumatic cilinders in to drive the rotation.
I have found a pneumatic cilinder that hase a rotation of 190 degrees, and is not to heavy or to big (match box size)
When I have more information for you I, will send it to you. (I am sorry for my poor Englisch, my homeland is The Netherlands)