You don't want the aluminum ones up here in the rust/salt belt. They corrode and snap off after a period of time. They generally break about the time you're trying to put air in the tire.
A "Grade Beam" is an 8 inch deep by 10 inch wide "Trench" around the perimeter of the slab filled with concrete and two rods all the way around. Then you pour the rest of the slab at your 4 inch depth.
Footer is not needed. Pour an 8"x10" grade beam with 2 rods in the beam around the perimeter with your 4" slab on the rest of it. You'll be perfectly fine. We do it all the time up here in NE Wisconsin. Never a problem.
Mine has worked great for years. The only thing I did was put the solid tires on it due to the fact that every time I went to grab it, one of the tires would be flat. Solid tires, problem solved.
What ever you do, do not drop that Snap-on light. They shatter. I've busted 2-3 of them. They're nice lights until you drop them. Not durable enough for shop use. They have come out with an aluminum housed one now. I have one on order to give it a try. We'll see.
Looking for a place to either order or go and buy cutting bits and such for my "New" to me lathe. Any suggestions would be appreciated. I've run lathes in the past but it has been a long time. Just picked up a "Filsmith" lathe and am going to start getting used to it again.