[eschaider]

Your model is essentially correct for a four-link suspension, although the actual illustration of the anti-squat line and instant center (among other things) are not correct. The concept you are attempting to use will not work on an IRS-suspended vehicle. It requires a stick axle and a four-link rear suspension.

There is an excellent tool for setting this up available from Jerry Bickel Race Cars. Again, however, it is for a four-link, not an IRS rear suspension. When I get home this evening, I'll post up more info and pics from the Bickel tool.