I spoke to lee grimes of koni, NA about this. he said that for most cases in amature racing/autox, the single adjustable would be more then enough but u had to make sure that the shock was valved for the spring that u were using with it. H also said that the adjustable compression was used mostly on vehicles in classes wher u couldnt change springs(stock classes) to esentially trick the car into thinking that u were using either a softer or harder spring . he also said that the difference between single adj correctly valved, and double adjustable was 1% on track time