Thanks, that sheds some light on the subject. I was a little confused about the difference between "chassis wiring" and "power transmission," but
this link cleared that up. I think we can safely consider R/C applications to be "chassis wiring," since the wires are generally exposed to air, and therefore dissipate heat more efficiently that wires in a conduit, in walls, etc. This reasoning would give 22 AWG wire a 7 amp limit, and 24 AWG a 3.5 amp limit. Either is good enough for the charging applications we use.