An IP-BPM system measures the beam jitter at the beam focused point of ATF2. It has been proposed to use a BPM triplet consists of three individual BPMs. We reconsidered the layout of the BPM system and the number really needed. We propose to combine two BPMs into one block and measure the beam jitter basically only with the two. An additional BPM is also needed for calibration and monitoring the resolution during the beam measurement.