I am currently trying to figure out what the option "LeafDistance" does when used in GraphLayout. There is no proper documentation by Wolfram. I posted a question on mathematica.stackexchange that is related

http://mathematica.stackexchange.com/questions/143154

In brief, I want to generate a KaryTree to construct a flow distributor. I want to be able to specify different parameters, including the length of all vertical sections. "LeafDistance" has an influence on the length, but I can't figure out what the parameter does exactly. The higher the value is set, the shorter the vertical sections become.