Wow, who dreamed up that crazy, curved design to act as a restrictor?

Betacrash... your idea sounds absolutely feasible.
Here's some free quick pointers for you guys that want to try to make your own based on what I learned while developing mine:
1.) When mounting from the top of a wood control panel, you will have to be extremely accurate with your screw locations. I found that being as little as 1/16" off can make the difference between not blocking the diagonals and not being able to hit the four ways. The reason you need to be so accurate is because the diagonals are hard to block by restricting movement of the joystick so high up on the shaft.
2.) Physically locating the restrictors with respect to the joystick's base location was the only way I could get repeatable results. This is where the mounting plate came from for my design. Believe me, the mounting plate was not added on a whim.
3.) I did look into the "drop in" type restrictors. The problem I had with these is related to tip #1. The joystick hole you will drill in your control panel may not necessarily located with respect to the joystick base. As I said above, I found that as little as a 1/16" off with your joystick hole/restrictors (with this method), and the restrictors lost accuracy or the ability to move in a 4-way direction.
When you are homebrewing your own, you are expecting to do some trial and error to make them work. On the other hand, when you purchase something, you will expect it to work as-is (I do anyway). To ensure repeatable & reliable results, I chose to design mine with functionality as the primary concern, and the aesthetics as second. I can understand that many would rather not have a mounting plate at all, and I am looking into a solution for that.
FYI - I do have a survey currently going at
www.oscarcontrols.com looking for input into the upcoming redesign of the spinners, mostly pertaining the to the Model 1's, but the Model 2's may be affected by the results as well. Curiously, the survey so far has been leaning towards keeping the mounting plate for the spinners!?! Go figure.

--OSCAR