I have been talking to these guys for a couple months off and on, going to swap out my springs for these. If you look at them they have a double spring action the main and a secondary. so the suspension is always under a load does not unload like a leaf would. prices are not to bad. a 2000# setup is about 450.00 Canadian. 3 year warranty and they are easy to fix.
Are those air bags or polymer springs (bumpstops)?