there is a website.. http://users.telenet.be/elvo/ that has a ton of information.. and if you use that information correctly.. you will begin to see what does what.. when raising the link, or lowering links.. its hard to read and understand.. however.. he shows pictures, and gif's.. that if you were to actually put it on paper.. and draw it out.. you would understand..

go to suspension, page 3, and you will see..

just some things i have noticed.. rod length adjust roll center.. very slightly.. and also depends on ride height..

example.. in this example.. lets say you keep everything the same.. ride height.. camber.. all that.. all we are doing is moving the rear upper camber link, and shortening, by changing location in the tower.. from inner, to outer hole

in the rear upper link.. if the link is lower on the inside.. vs.. out near the wheel.. slanting down towards the shock tower.. and you shorten the link, meaning.. move it out one hole on the tower.. you will slightly lower the roll center..

however.. if the link is higher or is slanting up towards the tower.. it has the opposite effect.. but very slightly..

This is the same for the front upper link as well..

Again.. this is just one small aspect of upper link length changes.. there are way more things that rod length affect.. but this is one small affect..