I attach a 3/4 in square aluminum with U bolts to the legs and then drilled holes and, using long screws, bolted it to the floor. My table had a leg come loose so, after having it rewelded, I also ran 3/4″ aluminum from the front leg to the back leg to minimize the stress on the legs. NOTE: My tub came out of a van so it has one short leg, otherwise I would have also run another brace to that front set of legs.

Rear leg brace.

Since the back of my tub was bolted to the wall divider I did not put lag bolts on this cross brace, but if the tub was totally freestanding I would have put lag bolts on this cross piece.