The OEI ceilings I have given are from QRH. Although for IAE engines there is no flattening of the curve between 25000ft. and 26000ft, the LRC ceilings are much lower in IAE. In IAE at 60Tons weight LRC ceiling is 5000ft. lower than CFM. I had earlier started a thread IAE VS CFM. So this is another handicap in IAE.