ok that soves the 1st problem, and any trouble splitting the siganl wires from the throttle or do we solder on a y adaptor?
Only a small problem. The Pies may be out of balance making one do more work than the other. Use your program cable to set the MP's even.
The throttle signal to both controller needs a voltage to be above .6v, .8 is normal with no twist, to not induce throttle failure mode in both controllers so watch what the load the 2 controllers may place onto the throttle, as this can bring down the no twist minimum voltage down a few points.
The throttle hall is rated at 7ma but I think from memory it can take 20ma load.
If you have problems here with the throttle load do try 2 throttles on each controller, a thumb throttle on the left hand and a twist throttle on the right.
I have built a throttle current amplifier as it seems, good for 100ma, when I was building a hall sensor tester. It never worked on hall senors in the wheel becuase I built with the throttle. Doh!
Give the split a try and if it isnt working well for you I can maybe guide you into how to do it.
You will need a multimeter and a little understanding how to do current tests and voltage tests if this splitting is not up to scratch.