I run Rocky mountains on my lightweight, 3 leaves on rear, with longer shackles I find the back flexes an impressive amount and handles great on/off road but does eat the bushes in a few years.
The front barely flex at all and sit a bit lower than the rear which is understandable with a winch and bumper, So I'm looking to try different para's on the front!
NB: If you do have extended shackles then lower your bump stops appropriately as I didn't first time and killed a set