To tag on to swatze's note, the angle of the brake lever makes a huge difference. When I first switched over to floorboards, I could barely reach the brake lever much less have any kind of touch with it. After adjusting it to a much lower lever, it is a lot easier to control.
I also run a Riken and have only once even had the hint of the rear end locking up. When I hit the rear brake, the beast stops NOW!!
Prior to going darkside, the Metz would lock up and slide out if you even thought about using the rear brake. I consider the Metz a safety hazard, imho.