I'm in Southern Ontario and built a 32 X 30 shop last year. My foot print was bigger than the town would allow for floating slab as well. But all i had to do was have a engineer draw me a suitable slab with proper rebar through out.
Drawing cost $400.00 from engineer
Doing a footing with...
I have used a jig saw with tape along the bottom guide plate not to scratch the stainless. Used this method on a fire truck worked perfect for 10" circle.