I havnt tuned my M5 apart from buying the adjustable stuff so i can modify settings. Thats means i dont get the sport brake kit but i do get the brake distribution kit etc. The M5 is fantastic despite its weight. I did the El Capatain 200 and it was so fun! Dont go to far away from stock settings i found, dont use ASM (I think its a bit of a cheat and slows you down) TCS about 4.
Spring rate 12.2/13.2
Ride height cant remember exactly but arouns 10mm-15mm above the lowest possible setting
Dampers bound 6/6
Dampers rebound 8/8
Camber 2.0/1.0
Toe 0/ -1.0
Stabilisers 6/6
Brakes 4/4
Leave tranny
LSD 5/20/10
Try these settings with no power mods and see what you think, i found it to be a great setting which works well with all the BMW's and similarly powered and sized car!