The crunch bars have same carb content as shakes,soup & porridge so apart from the 50 cals extra per bar, Its the same.
So with 2 bars & 1 other product (140 approx) you would be having just over 500 cals which is still very low & you will lose at same rate, i'm sure. Besides having 2 bars & 1 shake etc is far better than following a different diet or even cheating. If it makes the CD work for you, I would def have 2. I have read a few on here who have 2. I wouldnt have the chewy bars (highr carb) though because they will kick you out of ketosis & make you feel hungry.(2 per day would maybe).