The maximum usage rate of cetrimonium chloride is 4%. I use 4% in my liquid shampoo.
Cetrimonium chloride is one of those additives that you shouldn't go over the maximum on. I am not sure why, but I suspect that since it softens hair, it could soften it too much.
I believe regulations in the UK specify that it should not be over 4%. With LS, what this means is that you have to be sure to replace any water lost to evaporation.
With bar soaps, what this means is you should probably use no more than 3% since you will have some water evaporation during curing.