When I autocrossed my E36 M3 I used Scroth's very nice Quick Fit 4 point harness that clicked into 3 of the factory seat belt recepticals plus a supplied tongue that went attached to the outboard seat bolt -
http://www.schrothracing.com/store/t...ick-fit/qf-bmw. 4 points was very nice for autocross where you get in and out of the car many times. Afterwards, I would just detaching it and stowing it away in my helmet bag. Very nice.
Does anyone know of anything as convenient for the Z4 M Coupe? I suspect not, but thought I'd ask before I get a CG-Lock. Thanks in advance.