Back again Adam,
I have 3 leaf (2+1helper) and I suppose this is slightly light to have on the rear of my 109 hardtop, but they seem to work OK. I have the normal 2 leaf springs on the front, and have a PTO winch hanging off the front as well, and this does not seem to trouble the ride height, or the ride quality.
A good site to visit is www.ticonsole.nl as they are the manufacturers and have a great selection chart with all the info you could possibly need to set up properly. A good factory tour as well, and good explanation of how and why of para. springs. Generally just an informative site.
Pedal to the metal and GO.
Terry
