Personally, I would not parallel two PH-180s. I would do as SteveH says above and isolate my loops of track limiting each to 10 amps. Or one PH-180 per isolated loop of track. However, if you do choose to parallel two PH-180s then I would highly recommend using a Powermaster 360, that is what the PM-360s were designed to do, safely.
Attached is a manual for the Legacy PM-360.