1 Calibration final pion energy range. For now, I don't have objection to use 30-40GeV. So Let's stick to this range. In that case, I need a plot of photon energy distribution to get the anchor point. Those photons are from the pion that you used in the calibration. You can give me what you already had. 

2 Calibration should include  vertex information. Run15 vertex Z depends on pion energy. For 40GeV, it is close to -30cm, for lower energy pion, it should be a little bit closer to the 0cm. You could ask Oleg for the formular. Then turn on the FmsPointMaker option 'mVertexZ(1)' ,  and put the calculated vertex Z at StFmsPointMaker::Make() part

3 For what you present the high energy mass distribution. The suspicious eta peak might be from background of 1 photon from eta and 1 photon from pion, any easy way to check is to add the cut 'one cluster has one point (single point cluster)' back for 40-50GeV pion. Since in this energy region the eta photons do not end up in 1 cluster. So even you do not see pion peak any more , you should still see the real eta peak then.