Both the common ground and the decoder positive are NOT on the six pins. Those pins are track-power (2), motor-power (2), front light, rear light. That's it. (The positive power for lights on a six-pin comes by half-rectifying the track power when it is returned via the relevant lighting wire).
The more I hear about the 56xx and its decoder socket the more one dispairs.
Alternative small RailCom capable decoders include the smaller models from Zimo and D&H. Both tiny and may fit without needing right-angle pins.
( I disagree on Stay-Alives, they transform the running quality of smaller models in 2mm, 4mm and 7mm scales. These are models with all-wheels picking up reliably, carefully laid track with live frogs, etc.. And, I've had a fair few skeptics saying "not necessary" who come round to ordering retro-fits in their locos having seen what locos do. Its not about running over a sheet of A4 - a pointless party piece. Its about fractions of a second of hesitancy. ).
- Nigel
