4 piston calipers in rear?
Yes but there is no point for normal braking as you would lock the rears way before the fronts. The reason people do it is to run fiddle brakes on two pistons and the foot brake on the other two.
It would probably be too much for a trailer unless it is really heavy. Just Google for the adapter.
Pissing people off on the "net" since 1983.
Land Rover. Turning owners into mechanics since 1948.