The warp and the sag I think can be avoided which is why I put the casters directly under the vertical supports. I know what you are saying about casters and carpet. The truth is that once in place I don't really have any plans on moving the tank. The casters are more of a "just in case" option. In the event I do have to move the tank, be it for a leak or anything else, and even if I have to drain half of it, I still find moving casters on carpet easier than trying to drag flat bottom furniture, especially once it's made a footprint. I am going to have 6 additional adjustable feet for it as well for weight and stability. That build coming soon. In the meantime I'll try getting the pics up of the building I manged to get in on the weekend.