Welcome to TRS
Adjusting "spring" settings "up" makes for stiffer ride, so not the best way to get lift
Up at the top of each page here is a link to "HOW TO TECH" section
On that page you will find many "how-tos" by members
This section should be of interest to you:
http://www.therangerstation.com/how-to/suspension-and-body-lifts/
Also in the "how-to" area is this:
http://www.therangerstation.com/how-to/wheels_and_brakes/
Check out Tire Fitment
Point of suspension is to balance the weight of the vehicle on the springs, so springs can absorb bumps
using vehicle weight to defect the springs.
Too much spring for the weight and you might as well just weld some steel bars in for "suspension", lol, vehicle is too light to defect the springs.
And thats a problem "they" run into in Trucks, rear weight of Ranger pickup trucks can very by 1,000lbs, 1/2 ton rating
If you spring it for 1,000lbs then it will be over-sprung when bed is empty, and it will have a horrible ride, which some do.
Trick is to use empty weight springs/leafs and then add an overload leaf that doesn't touch the frame until load exceeds say 600lbs
So you get the good ride, and good traction, when bed is mostly empty, but can carry a load when needed
Traction happens when tires are on the ground
If there is too much spring then tires lift off the ground on bumps, and you loose traction
And that applies to front or back wheels