Ive fitted a full cossie 2wd set up to mine, and theyre not all that IMO. The master cylinder isnt up to the job, needs to be larger otherwise theres a noticeable difference in pedal travel (although without the rear discs it will be fine), although i havent really properly run them in or had a good drive in it yet as i need to MOT it.

Some of the comments above are feasable, lots of people have the ST170's, and the standard calipers with cossie pads make sense surface area is what its all about!