Well, had a chance to continue working on my flightstick modifications today. I finished all my fitting issues. The initial pics did not have the 16000.M's PCB in place or the PCB for the thumbstick in place. Today I finished removing the hat switch from the 16000.M's PCB, trimmed the leads from the trigger switch on the top of the board, trimmed some more plastic from inside of the handle to make the space I needed, cut 2mm from the top of the thumbstick's PCB, cut another 1mm deeper into the sides of the thumbstick's PCB (I have a semi-circular cut on each side with a little notch more taken out towards the top), soldered the thumbstick to it's PCB, trimmed all the leads that passed through bottom of the thumbstick PCB, and was able to fit it all together back in the 16000.M flightstick.
I need to place electrical tape on the bottom of the thumbstick PCB, run 4 wires up from the base of the 16000.M, solder the thumbstick PCB to the wires, and the wires to the teensy control board, cut the holes for the USB mount, and test out all my electrical connections. I might add a dab of hot glue to keep the thumbstick in place a little better, and I then need to program the control board to properly read the inputs from the thumbstick and act as a USB input device to Windows.
Really the hard part is done at this point. Running a couple wires is pretty easy compared to cutting into the 16000.M to make space for the thumbstick and PCB. I will be taking pics before I put it all together. It didn't come out too bad. Unfortunately I wasn't able to center the thumbstick as nicely as I had hoped due to the internals in the handle. I trimmed as much as I could from both the thumbstick and handle without losing structural integrity. I am still about 0.5-1mm from being centered, which unfortunately leaves a small gap on the one side of the thumbstick, but it is what it is...
Also, I am disabling the green LED on the base of the flightstick. It is just annoying as can be. And I just have to say getting that damn hat switch off the 16000.M's PCB was a major PITA!