This isn't exactly a large scale question, though I think it probably also applies. I have a Bachmann On30 loco with a Micro-Tsunami decoder, and I'm not a big fan of electronic chuff synchronization. Consequently, I've installed a chuff cam from Tony's Trains on one driver. Does it matter which side of the loco that driver is on - i.e. engineer's or fireman's side? On this particular locomotive, both drivers are insulated from the axle and power is picked up by wipers on each wheel. My concern is whether or not it matters to the chuff circuit which rail the signal comes from.