Actually, you'd need about 5'6" of tubing, and cutting it straight would be quite difficult, but there are similar items out there that would do the same job. If you are crafty and ambitious, then go for it.
Personally, I think those Tuba Feet are ugly and totally useless. They would probably protect the horn if you only used it once in a while on a nice, smooth hard surface, but without complete bell coverage, you would end up with scratches on grass, concrete and asphalt, which is where you need the protection anyway!. Also, anything too heavy or thick around the edge of the bell would cause distortions in the sound, which is worth a few scratches in the end.