Huscarls (but not thegns) in shieldwall, select fyrd and great fyrd may be mixed in the same TuG of 6,8, or 9 elements. If used, elements of huscarls, select and great fyrd must be easily distinguished.
Elements in a mixed TuG including great fyrd may not be given the Shove characteristic.
given that the first two ranks can have shove,
given that shove does not require several ranks to have shove,
given that a unit in 2 ranks can shove,
i fail to see why the two first ranks would loose the shove characteristic because the 3rd rank has less stamina to push forward, would the 3rd rank not just follow?
It is nothing to do with the ability to Shove. It is to get the right feel. Units with Great Fyrd are essentially defensive, not offensive.
Richard