On the 128 sedan I used to race, I ran a three leaf wagon rear spring along with a rear sway bar. That helped not only minimize understeer, but also help minimize front wheel lift, which is a real speed killer if you're not running a limited slip or welded diff. Ideally, you would be lifting your inside rear wheel in hard cornering like a old Mini. The problem with the 128 sedan is you have to overcome the large front sway bar, so you have to go real stiff in the back to minimize understeer. On my current race car, a 1st Gen Civic, I'm running no front sway bar. The plus to coil overs is that it's easier to set corner weights. No as critical in street cars used for occasion track use. By the time you've got your coil overs dialed in, you'll be shaking some fillings loose.
