My Clymer's and Haynes say the float tab should just touch, not depress, the shutoff valve when parallel to the carb body--that was too high because I had fuel leaks on both sides. So I tried to adjust the tabs while the carbs were mounted to where the gas just shuts off just when floats are parallel to the carb body--talk about a trial of patience but finally got it done and all is well. Lesson learned.

I have always gone with - the fuel just shuts off when the float reaches parallel with the carb body. 

Snowbum has an actual depth measurement somewhere in his writings. You measure the depth after removing the bowl, with the float volume removed. Seems like overkill to me.