I drilled the inner left floor stiffener to the floor today. This was accomplished by clamping the stiffener to the firewall and F-704 brackets. The image below shows how I clamped the stiffener to the F-704 bracket.
The firewall bracket clamp-up strategy is shown below.
The stiffener will need to be drilled to the brackets, but this will have to wait until next time I make it to the hangar.