Last night in our blog we posted reasoning for the exact elevation we are trying to lift and stack.
http://blog.spectrum3847.org/2015/01...4-bar-cad.html
Summary, lift should be able to elevate an object 4.5ft. Allows you to stack a tote on top of 3 totes on the step and allows you to put a container on top of 4 totes if you are grabbing it by the lip.