Does this help:
http://forum.mysensors.org/topic/748/manual-assigning-node-id-s-for-network-with-repeaters
I agree with you that the serial messages are not perfectly documented, but realise that this site has been made (as far as I know) by a bunch of people that share their 'love' for home automation.....
boozz
@Jason-Brunk small value resistors can do the trick but you better try two silicon diodes 1N4001 or similar in series with the power line. Each diode give you around.0.7 volt drop.