position of mast base on the board

[izzykatz]

Hi,
I sail for some years already, but still did not find a good answer. on my F2 board there were marks of sail size - 6.4 forward, 4.5 backward. I therefore conclude that as the wind gets stronger the base should be shifted backward. Is this correct? what are the parameters and how they affect the base position? how to find the optimal setting for a certain wind/sea conditions?

Thanks
Izzy