The P2 brake controller would work great on your 20,000 lb dual axle trailer, as long as the braking system is a 12 volt system and there are no more than 8 brake magnets in the trailer braking system.
Typically tandem axle trailers with brakes on both axles have 4 brake magnets, but some heavy duty trailers, possibly like your 10 ton trailer, have dual wheels on each side of the axle and could have 8 brake magnets installed. Just make sure there are no more than 8 brake magnets on your... view full answer...