Frank, the board is 17mm wide and 42mm long, but there is also connector running forward, so you must add the connector size to the length. Height is 8mm but if you use also upper connectors (twin, LG, LED) you need 10mm.

Also remember that is good to have it tangent to the circle, not to the model, so if you use larger yaw (LO offset) it is good to install opposite offset to the board so that the sensor is tangent.

I usually mount it to channel of (almost) fuselage width, 15mm tall and I mount it to slider so I can shimm or angle it as necessary on the slider.