As far as i know there are two things you can do with leave springs (not sure if it applies to all landys) these are;
swap the metal (leaves?) round so the top one goes on the bottom and the bottom one on the top etc.
or
move the mounting blocks lower or higher on the axel increasing or decreasing the ride height.
I think the first one is what the guy was talking about as its quite had to convay and understand, it does give a stiffer ride and some other beifits that escape me at the moment, however i would'nt bother with it.
M_O