I think you can go up to 6 cSRM2s without ghost heat. So you could fire groups of 4 (arms) and 5 (torso). http://mwo.smurfy-net.de/equipment#weapon_heatscale
good call, I thought it was 4 c-srm wide. Build is easily changed exchanging 0.5t of ammo in the CT for the 9th SRM2.