I have an '01 Cobra vert with the H&R Super Sport springs w/ '00 Cobra R Bilsteins. IMHO, it sits too low in the front - I do hit high spots in the road with the K member - like peaks or high road repairs. Have to be very careful. Other than that, it looks killer - get lots of compliments. Ride is firm but not jarring or harsh. Rides much better than my fox with the "C" springs. As for putting them in, the front is the same as all fox platform cars - I didn't use a compressor - just undid the strut and stay bar ends and lowered the arm very slowly. Be careful here.
The best way to do the IRS is to remove the subframe bolts on one side at a time and let it down slowly - springs will nearly fall out. Pay atrtention to where the stockers are located and put the new ones back the same way - I marked mine. To do the subframe bolts, you will probably have to loosen the exhaust (I didn't remove mine, but had to move it around). You may have to undo the lower shock mount as well - can't remember - been too long. I tried doing this with a compressor first, but because the H&R SS's are progressive, the compressor bound up in the dead coils and I couldn't remove it with weight on the car - hence, removing the subframe bolts. This proved much easier than the other approach. Getting the subframe back in is a PITA, but doable with one guy and a large pry bar - that's how I did it.
I used the stock rubber isolators on both ends but I think I'm going to replace them all with the poly ones (MM makes a revised version for the IRS pockets) to try and raise it up a bit - tired of the risk of hitting the K all the time. Good luck.