Balustrade spigots - fixing

Hi. We have a balcony with frameless glass balustrade - held on by spigots, these things Spigot Surface Mount - Polaris Hinges l Pool Gate Hinges

The construction of the balcony is a few beams from structural steel, lvl’s at 600mm intervals, then Scyon exterior flooring (which is compressed cement sheeting, I think 19mm), waterproofing, sand and cement screed, more waterproofing, then porcelain tiles.

I need to add a couple of panels of glass. The existing panels were done by the builder and I have no idea how the spigots were fixed. It was done before the screed and tiling went on.

Now I want to know how the new spigots should be fixed? What are the rules? Can they be fixed just to the Scyon sheet, or do they need to be screwed into some timber members ? Etc.

BTW: I won’t be doing this work myself (too chicken) but as usual I want to understand the basics before talking to installers.

Cheers
Arron