I have also designed my own foot plate for the robot. As the foot plate that comes with the Rero platform does not allow one to adjust the lateral position of the plate with respect to the "Wide U-joint". The picture below shows the 3D printed foot plate attached to the Wide U-join, which form the ankle of the bipedal robot. The stl file can be obtained from Thingiverse:
http://www.thingiverse.com/thing:924626