Okay, I'm clear on what ackerman angle is and does, but what goes into setting it?

TIA

It is built into to the steering arms. I wouldn't get too concerned about it on an offroad vehicle especially with big tires and offset rims. The intersection of the imaginary lines drawn through the ackerman angle on each front wheel should cross at a point that is the same distance as your wheel base from the front axle centerline. (in front or rear, doesn't matter)

Ackerman becomes a moot point when you have a full time front locker, and even if you are open the terrain we are on negates it, for the most part, also....

I've bin contempating a Hi-steer set up but wanted the same info first, recently got a line on this
.http://www.rctek.com/handling/ackerman_steering_principle.html
hope this helps, RC cars are just scaled down, no reason for it not to work on a full sized vehicle. I compaired it to what I have and it shows exactly Y my truck does what it does (Tie rod ends on mine are too far apart). it only takes 4 measurements to figure it out. Big offset tires will change things a bit aswell. To make the RC formula work exact, your tire center lines would have to be same as your ball joints. Just add acording to your tires.

Cool thanks.

Sounds like it isn't a big concern to me.