Also, depending on how much taller you needed, you could try adding four extensions to the footings of the support legs. Any tube with a slightly larger inside diameter to the outside diameter of your leg poles.. or even it you had thick pvc or something and could lathe off a layer so that part of the pipe would slide in snuggly inside the base of the original frame legs.. add a certain length to them. Heck, you could probably use a 3D printer to make tubes that have the top 4" or so smaller diameter so they slip into the current bars to add height. Just some ideas...