Baffled tank definitely better. I have a Prochem set up with a long tank down one side, un-baffled, the water slams up and down it enough to knock the lids off sometimes. Watch your weight, though - 500l. of water weighs 500kg = 1100 lb, or half-a-ton! Don't want to run foul of VOSA or anything, plus if you have a prang overweight your insurance is stuffed....