A local layout has 12 AWG bus runs of over 70 feet to a distribution panel. 12 and 14 AWG buses head out to the track from the panel. Absolutely no problems at all.
The NCE Power Pro manual has the following recommendations:
“For the hobbyist wiring up a new layout our suggested wire sizes based on voltage drop are:
Runs to twenty-five feet #16
Runs to fifty feet #14
Runs over fifty feet #12
For best results on long runs (over 20 feet), twist the bus wires about three turns per foot.”
If you haven’t purchased you main bus and sub bus wiring yet, I recommend you go with stranded rather than solid wire. The electrical differences between solid and stranded wire are negligible in the NCE environment. The flexibility of stranded wire compared to solid makes it the wire of choice.