I have the H&R lowering springs an barely made the 1.5 deg neg camber in the rear. My pic shows the rear at over 2 deg neg camber before alignment. Much prefer the look and cornering. Over heavy terrain, you will bottom out the suspension though.
James Greer

 

Thanks for the link Houston996:

Too bad they don't fit 996 '05 C4S. The kit for C4S's are $2,500 !!! Comparable to PSS10's. But, in general that is what I'm looking for, just a mild drop of around 20 to 25mm.