Programming a BMS for a LiPo battery?

I'm using a 3S LiPo battery for my drone project and want to program the simplest possible BMS just to prevent the battery from over discharge. I want to do this by just measuring the battery's voltage because I don't have time or place for more components.

So if the battery is at cca 12V when full, at which voltage should I stop discharging it (or rather send a signal to my drone to land slowly)? Of course I have to consider the voltage drop when the four brushless motors start spinning.

The image below can probably help me but I don't know how to handle the mentioned voltage drop.

voltage chart

Can you battery knowers help me with this :)

Sorry if this is the wrong place to ask this.

Thanks in advance :)