I'm surprised nobody has posted a diagram of a MacPherson strut roll center. I took this from my vehicle dynamics textbook. It will help you visualize what can be done to raise the roll center.
From the diagram you can see that you can raise the roll center in several ways after lowering:
1. raise inner joint
2. lower outer joint
3. Increase shock lean towards inside
4. increase track width (seems counter intuitive, can someone check that out)
Last edited by WDE46; 10-03-2012 at 05:56 AM.
Reason: corrected language for raising roll center :-O