i tabbed it under all of the holes. i used a piece of 1/2 starboard to give the screw plenty of meat to bite to.
the gflex is GREAT stuff, i use it all the time for small projects. i used to it to adhere a piece of starboard to my transom for my transducer. no holes in the transom. tducer attaches to starboard only. used it to attach small strips of starboard to deck in my small whaler to hold fuel tank & battery box in place, etc.
i like the thickened better than the other, seems everything i do is vertical.
this is a shot of the "clamps" i used. just a cross section of pvc(2") with a small piece cut out. you don't want to clamp to tight, it will squeeze out all the epoxy