A friend has a bench top 12x 36 that he built a base for out of square tubing, with diagonal bracing and leveling screws. It seems to be a lot more rigid than a sheet metal base would be, and has worked well for a number of years. He spent considerable effort leveling and testing his machine, and when and if I get a lathe I will undoubtedly do the same. When he first built the base, it was so rigid that his adjustments at the floor did not translate to the base of the lathe. What he ended up doing is building screw adjustments into the diagonal braces so that he could tweak the stand to level and tune his lathe for bed twist. I believe that the time that he spent doing this was a good investment toward the quality of his work. He purchased a high quality level that is long enough to go across the ways and which is sensitive enough for this kind of work, and since concrete garage floors are not as stable as they might seem, he checks the lathe from time to time.