Stan, I think you are overlooking some of the things I mentioned. But, go for it, if it does not work, then you can explain the differences in the ground potentials.
Jim, I gave you my best recommendation, use a magnet and pickup... if you want to use the existing chuff circuitry, I think some more investigation is in order.
Since Stan has chosen say "forget about the schematics" obviously he knows exactly how to make it work. If you follow Stan's advice, please be sure to ask Stan if you have problems.
Regards, Greg
(Stan, it was ME that was going to look at the schematics, and I AM good with electronics, and the implied insult is registered, but just go ahead and make it work for Jim, that's all that counts)