One thing that I didn't like about the copilot stick was that there was a small amount of slope in the telescoping fitting. Also, with the control grip, I felt it important to restrict the rotation of the grip. So I set out to figure how to secure the stick to the base.
I went to the local Lowes Aircraft Parts Center and found a couple of PVC fittings that would allow me to have a treaded retaining ring to secure the stick. I cut a hole in the cap and cut off the threads of the fitting. After working the holes to just fit, I glued the threads to the base tube using epoxy cement. This gave me the ability to secure the stick, but it did not provide anti-rotation.