Your build is not that much more heat efficient, mostly because the external DHS dissipate less than the internal ones, but it's hell of slow (7% cooler but 21% slower). I think the XL225 will be better. At the cost of 0.5t armor, you'll be 7% faster and slightly cooler (3%): Or, you can go almost full armor with only a minor dissipation downgrade (4%):
My version: Downgraded to PPC for the cooling. Bump the engine all the way back to XL255, that allows for Endo and FF, thus you can fit more armor. The ERPPC version is not bad either. Hotter, but quite ok at long range since you don't use the ML. At close range you do a bit of heat managemnt with th ERPPC.