Seeking wisdom from those who have installed a lift

It's not only the thickness, but the composition and where the rebar or reinforcement is. Seek out the requirements as set forth in your lift. Most of the ones I've seen require minimum 4" 3K psi concrete...that's what mine is, and I've had no issues. Overtorquing the anchors, poor reinforcement, and porosity in addition to overloading is what makes the floor spall crack and fail.

My footers are (i think) 18", so if yours are 12", you might wanna find a way to verify what you have for a pad...if it's anything less than 4" consistently, you'll need to remedy that first...

I have a 10K overhead beam Atlas lift in my 30x40x12 shop. There is always a car in the air and one parked under it. I had to use the lower of the two beam settings because it was about 5" too short to accommodate the higher setting for the crossover cables...YMMV, but if you have less than 10' walls, choose your lift wisely as most of them require a minimum of 11' walls, unless you go with the non-joined versions specified for low ceilings

I also check the anchors periodically to make sure they haven't shifted or loosened.

Make damn sure your posts are perfectly flat (shimmed) before drilling/setting anchors

Measure twice, drill once-can't say this one enough...if you're not positive, remeasure. Everything needs to be square, parallel, and plumb

The lift will always be a little in the way because of it's footprint, but give yourself at least 24-30" in every direction...enough room to push a toolbox through or carry something somewhat awkward.

Depending on the model, you'll need at least a 30-40A 230V dedicated breaker...make sure your box can handle that.

Probably the best thing I ever did for my shop...