I hauled rebar for a living I would go with #4 (1/2") rebar on inch & a half concrete dobies that puts your bar close to center of your slab 12" - 16" on center and make sure you hold bar 2" - 3" from end of forms.
You'll be happy you did.
Scored a major amount of honey do points the little woman bought a import tractor seat off ebay and wanted me to turn it in to something for her garden so I took an old patio umbrella stand and a 2" piece of steel pipe and with a little welding and some paint I came up with this.
Built a potting bench and bird houses for the Mrs. out of old redwood fence boards and I got a old planer on CL for free and a craftsman table saw
my wife loves them and I scored big time points :thumbup: