When I mentioned spill flow, I was referring to the 'excess' flow from the HP gear pump, which due to compression and pressure drop across the regulating valve imparts an increase in the fuel temperature regardless of whether the fuel is acting as a heat sink for the FOHE. As the gear pumps provide flow proportional to the gearbox and hence NH speed, the available flow is always more than the required flow to maintain selected N1, EPR etc. This warm excess flow is then re-introduced upstream of the LP pump (impeller). What seems to be important is where it is re-introduced
I am in no way saying that the RR FOHE re-design will completely address the problem, as for now the complexities of the issue are not fully understood.