Per Eibach R&D:
On 2003 Cobra's their springs lower the front .6" & the rear .9" on a stock vehicle with 3/4 tank of gas.

Be sure you do not tighten the control arm pivot bolts when the suspension is in droop as this will preload the bushings and cause an "over height" condition. Tighten the bolts when the vehicle is on the ground at ride height.

Another area to watch is the indexing of the coil pigtail into the pockets...just a little off can make a huge difference in ride height.
This exactly what the tech told me. Then I explained that I took out the 2 bolts that hold the entire IRS up to put the springs in. So there was no way that I tightened the control arms to much. He replied that "something else is wrong with your car". He was a great help! I will probably put H&R's in the rear now. On a side note, are you going to Coastal Saturday?