yes, short cable is good. and yes, tip and sleeve of the jack will give you ball park readings. wont be 100% accurate but close enough to see whats going on. the rail coil should be like 5.5k, the p90 about 8k. i do notice the rail coil to have less volume than the p90 coil, but i kinda expected that. just like a vintage strat pup has less volume than a vintage p90