You mean the square peices that tie the front and rear plate together? Or the front and rear plate? I'm actually hoping there is a very slight amount of flex allowed since it's designed to work with the brake. If there's no give at all, the servo will fault.
One concern I do have with those square plates is the mating surface slipping. The pressure of the bolts might not be enough to prevent that. I figured I could use an appropriate loctite on the mating surfaces to prevent shearing, butbi could also make the peices mate differently to prevent it, sort of a taper to lock it's position when tightening down