Personally, and for my own piece of mind, I would be cutting a roughly 30"x30" section of the slab on each side and digging a hole for a footing. put a rebar cage in the hole and drill into the edges of the existing slab and using some epoxy grout, install some rebar dowels that protrude into the opening about 6" all around. Then purchase some high-strength anchor bolts and insert them in the hole tie-wired to the rebar cage. Make a template out of plywood for the bolt layout to hold them in proper position. Fill the holes and finish with some good high-strength concrete (5,000 psi). Remove the template and finish around the anchor bolts.
Sounds like overkill, I know. But am not so fond of the idea of a two-post lift rolling over!
My 2c