watch some racing, ideally you would have a completely smooth under body tray so that turbulence is minimized at speed. This will function to minimize lift or maximize downforce. Creates a low pressure void under the car where you want it. Young guy at the shop that my e46 was put together is working on a prototype for a full underbody for the e46 m3 to tie in with rear diffuser and front lip. may see it on PrimeBMWs car at some point.
02 Tiag e46 M3|6MT|GC plates|MCS c.o.|GC bars|GC race control arms|GC bushings|BW eng. & tran. mounts|subframe kit|BW race shifter|BW Jaffster|Euro header|BW exhaust|K&N c.a.i.|Epic race tune|Rouge pulleys|Seibon CF hood|CSL bumper|ST-40|XR-2|SS lines|half cage|Recaro profi|Profi 2 harness|BMWpedals|BW studs|