According to the manufacturer, 20 droppers are the maximum

I have more than 20 droppers on it, I can't tell you what the maximum is. But there are only 20 droppers in the set.

I think about 5 pieces should not be a problem. The difference in height and the total length are crucial. I find the pump quite powerful. I have to overcome a height difference of approx. 2 m at the end of approx. 8 m and the pump manages that.