Chris,
My Phantom is pretty heavy as Phantoms go, it weighs just over 3 tons, plus the trailer, so I'd guess at nearly 4 tons total trailer weight, despite this, the Pajero pulls it remarkably well, it has adequate power and considering it's short wheelbase, it's pretty stable when pulling such a huge weight (probably 1.5 tons overweight)
The brakes on the trailer that the boat is currently sitting on don't work, so stopping it, especialy in the wet, is a bit hairy.