Stock springs were built to give a soft cushy ride. Soft cushy springs sag, especially when loaded up with gear or pulling trailers, etc. I imagine Toyota gets 100 complaints about a harsh ride for every one that suspension is too soft. Or use stock springs ad add air shocks or air bags to add lift and load capacity when needed.
A whole bunch of 2nd gen suspension reviews on the Toyota section on 4x4wire...

Cranking t-bars is no different w/ ADD.