For the IRS arms the BEST solution for ride height is the aluminum spacers from BMI. They replace the plastic spacers that come with the arms and come in .5mm increments. It is a bit expensive to get the whole set but it is worth it. The spacers fit tight to the screws and it is my belief that this tightness helps to reduce arm cracking that many people find with the IRS arms. I believe that the spacers reduce how much the screws can deflect in a crash. The other options given above are also good solutions.