I put an ER-Medium in the head, it synchs nicely with MRM range and is at the same height as the MRMs. You can fire them all togetehr for for 85 alpha. I downgraded the Mediums Lasers in the arms to ER-Smalls to save some tonnage, the MRM-40s are hot and the arms are low slung so i only really use the ER small lasers for fending off lights.