Hey - I used a stick extension for my warthog for awhile and also did not have a good mount at first. I already had a simple "pit" using pvc piping (it holds a side-stick, throttle, and pedals). I used a plan from roger doger aviation (I think). To use the warthog, I simply built a center stand using PVC pipes, a few pieces of wood, and some velcro to stick the warthog on it when needed. I added connection from the center mount to the pvc pit to keep it in place when in use. It worked pretty darn well. I decided to use my warthog as a side stick for now, so now this center mount is a good foot rest, or holds random items when I'm out of desk space :).
Anyway, just an idea. If it could help I could send some pictures. In any case, good luck on making/finding a center mount!
Also - the stick extension was very awesome. I did about a 4 inch extension (home made) because that's how long it needed to be with my center stand. I had the stick base as far up and as close to my chair as I could, with the large base plate going just under the chair.
I would highly suggest just buying the stick extension - it was a bit frustrating to build my own, and I don't think it was perfectly straight ;), and I like that he already has plugs setup. When I go back to using center mount I'll definitely get one.