Here is a decent starting point for low/med grip carpet that I've been using. My computer's being dumb with PDFs.....
Spool, 1.5FF block, 1.5 split FR block (no shims under blocks), medium wheelbase, 2mm bumpsteer, 1mm ackerman, 5mm ride height, 2mm uptravel, 1.5* camber, medium camber link (4mm inner, 0 outer)
Front shocks - Yokomo black spring, 450cst/3hole piston, 0 rebound, shock in 3rd hole on tower
1k rear diff, 0.5RF block, 3.5RR block (no shims under blocks), fully long wheelbase, 5mm ride height, 2mm uptravel, 2.5* camber, medium camber link (4mm inner, 3mm outer)
Rear shocks - Yokomo black spring, 450cst/3hole piston, 0 rebound, shock in 4th hole on tower
If you can run the above setup with the RRS system it gets even better. Set static toe to roughly 2.5-3, and "compressed" toe to 3.75 or so. This will let you drive the car a little harder.
If you want a more stable car or a bit more push try these......
LTCR, Sweep/Sorex, front shocks to 4hole OR Yokomo blue front spring, 3.5* static rear toe
If you want to free the car up a bit, or the grip comes up well, try these.....
Mazda GX/Speed6, harder Sweep or Solaris Medium, .5mm shims under arm blocks, rear shocks to 3hole, 2* front camber, 400cst oil in shocks
I also tried Serpent Gray springs all around. The only difference I felt is that the car lost a tad bit midcorner steering but was a little more responsive all over. Black front/Gray rear would be decent on a bigger or more flowing track, but it took away the entry steering that I can't get enough of, which I like on tighter tracks. I do not have Serpent White springs to try at the moment.
My fastest runs were on the above setup with the GX, Solaris, 2* front camber, 400cst oil in shocks, and more rear uptravel. I drive pretty aggressively though, and was using handbrake liberally to help stabilize the car going into turns (which can be a huge driving "aid" on really low bite). On-throttle the car was pushy enough that I could drive harder out of the turns and through the sweeper.
Also, on low bite carpet don't be afraid to dope the hell out of the tires. I was cleaning with SXT, doping 15min before my run, then adding another coat about 3min before I went out.
I think that the lower the grip, the more important the tire/body combo will be, especially with regards to how you want the car to handle.
Hope this helps