i've been reading the book written by the doctor who created Cambridge, and original trials to speed weightloss in obese patients, conducted in hospital, involved zero calories - just a drip containing vitamins etc. but there was a serious side effect - death - and average weightloss was exactly the same as it is on SS (3-4.5lb a week).
what he discovered was that we need a certain amount of protein, carbs and fats to keep us going - specifically, to keep your muscles, including your heart muscle, from wasting away to a dangerous extent. if you have three cambridge packs a day, you are having the minimum required to keep you alive and healthy. if you have less, your body will begin to shut down functions (such as hair growth), but more worryingly, your body will use the tissue of your organs, including your heart, for fuel to such an extent that it may stop working.
I know you want to lose more than a stone a month - and you might do that - but the fastest way is by sticking to SS 100%. keep up any exercise you're currently doing, but don't do any extra or your weightloss might stall.