You are flirting with danger, and so far you have been lucky. To cook a little an then allow to cool outside is a bad practice. These chix are loaded with bacteria an salmonella fall off.
Why not fully cook right before service? You don't have to put in fridge this way,Its fresher and certainly more sanitary, and they wont be dried out. Estimate what you will sell by checking back on customers purchases over last 3 months.