Yes... Only in "emergencies" would it be ok to have more, ie if you'd break the diet without it. According to something I read it can affect the absorbtion of meds etc so best to stick with the recommended amounts! X
I think you stick to 1.5tbsp because of the carb content as well, on attack you want to have as much pure protein as possible so you lose more without the carbs messing the loss for you!