These vehicles do have a very high ground clearance and the base of the flat bed is very high. this raises the centre of gravity. If you put a decent amount of water at that height, you're just asking for trouble.
If you take a bend just a mite too quickly or need to swerve for any reason, you're going to roll - and kill and/or be killed.
Stick to a van with a nice low floor and consequent low centre of gravity.