I cant remember precisely the width is about 4500 I think I put them at around 800, I just used blue plugs and batten screws to hold in place. Since the weight of the deck itself and no upward forces I went easy on the fixings to the concrete. I have since made some additions for those who are interested.
Simple cantilever to support BBQ & stone benchtop, plywood flooring, cabinetry to come shortly.
Cantilever deck extension for built in BBQCantilever deck extension for built in BBQ