Knowing how long others cut their steerers will do you no good since you don't know if they have their bar height set the same as you want.
You need the headtube length and the stack height of the headset you plan to use. Then add the height of any spacers you want and the stem's clamp width to calculate the total steerer length.
Here is some data to get you started: My 56 cm Co-Motion has a headtube length of 135 mm and my 57 cm Litespeed has a headtube length of 150 mm. both bikes use conventional headsets, not integrated.