My Work in progress of the UT-AT as seen in Episode iii. I still have to add the front end armour, the side fitted cannon and the top gun. I also have to add the repulsorlift feet and the rear gunner seats in addition to the front end troop area (for 20 troops). The model, as you can see, is colossal, being about 20" in length. At the momment the exoskeleton is lighweight as is the body, so it does not yet weigh as much as the Lego AT-AT (about 1 1/2 lbs.
As you can see I have added the front end armour and guns in addition to other small details. I have yet to add the repulsorlift feet.