How do you attach a heavy camera (Canon EOS 750D / EOS Rebel T6i) to a tripod with an Opteka GH1 ?

What additional doo-dad or alternative doo-dad will make them happy together?

The "rail" part of the Opteka GH1 and the mounting square screwed into the bottom of the camera only overlap a few millimetres, because of the width of the camera and the additional width when the microphone is attached to the camera.

The camera is so heavy that it can only droop.

So, it's held in position with a bunch of random objects held in place by a stack of boxes next to the tripod.