#1 and #2 both relate to coarser grain which results in higher speed. #4, slower addition rate, results in higher speed as well, this is due to more time to form larger, more perfect crystals?

With my peristaltic pump, I can go from addition rates of about 3 ml/min (with my current tubing size) on down to about any excruciatingly slow addition rate you can stand to wait for. Is there a practical limit as to how slow the addition rate can be made?