I was thinking... (or not...)
Seems to me, changing the difference in temperature of the coolant, with lower theromstats, bigger fans, etc. Is less important than the total volume of coolant flow. Coolant at too low a temp entering the heads only makes the thin walled problems worse. Since hotter coolant carries away less waste heat per unit we need lots more units.
So what options are there for upping the flow through the heads? Maybe polishing some of the water channels? Better hoses? Water pump changes?
Just brainstorming here, DasWaff