I finished the MCU version. The only real advantage is that you can
hold the carrier in place firmly against the input rollers, then
press the Continue (X) button on the printer. The printer will pause
for whatever time you program it for (I use 1 second) before
attempting to pull in the carrier. This gives you time to be sure
everything is centered and square. Also, if it doesn't "grab" the
carrier you don't have to remove the carrier - just press the button again.
The mechanics are a bit simpler - no exit sensor, simpler center
bracket. The sensor is a reflective IR sensor.
The downside is you have to buy a sensor and either make or buy an
mcu board. You can use one of the Radio Shack "breakout" prototype
boards (stock # 276-159). I should be able to get everything online
by Friday or Saturday.
If I had a head count of anyone who wants one I could probably supply
a very simple 'kit" of parts for a modest sum.
Mark