Greg, some guys are running as low as 26.5", but that's probably the lowest you can go and not worry too much about bottoming out. I'm running about 26.75" on all corners and I still have 4.5" of clearance at the
oil cooler shroud as well as the bellhousing and
oil pan. Never had any issues at that height and the extra 1/4" makes a big difference in the looks department.
Also don't forget that the more you monkey with the coil overs in adjusting ride height, you do/can throw off the weight balance of the car and the alignment, accordingly.
-Dean #747