Sweet gearbox!
You might want to consider using one pneumatic cylinder instead of 2. If you put one in the middle and hook both shift bars to it, you get the same effect as two, but use half the air. (unless of course you're planning to use a compressor or utilizing the space between the two cylinders)
Just a thought; our team did that with our pneumatic shifter this past year and it worked great. It helped us with weight by eliminating the extra cylinder and potential air tanks.
