It would seem that the best place to put them is about where the legs touch the ground. An easy way to check that is to place three pads on the ground where the legs will touch the ground and place something like oil or butter or paint on the pads. Then place the bottom section of the WSM on the pads. When you turn the base over, you should see marks from the grease or paint to indicate where the legs touch the ground. If nothing else, this should be a good starting point. As for what type of drill, I would use a cobalt drill. They will drill through stainless steel so the legs should not be a problem. This is the type of bit I use for most things. They are not cheap but they do work. One more thought on the wheels, you can use nuts on both sides of the legs to allow you to level easier. Also, lock nuts might be a good idea so they won't loosen. Good luck.