I don’t know exactly how much total expansion there is; but I know that starting with about 3-4” in the bottom of the overflow bottle, no coolant goes overboard from there when the coolant temp is up to 220F, so the total is less than a quart.  At some point I will leave the cap off the overflow bottle and observe the change in the coolant level from cold to hot.

Al

Al, I've seen photo's where there is a filler cap on the return line before the pump, but not remotely located like yours, is that the similar but simpler approach you are explaining?

If this is different again - is there any advantage or disadvantage with this system, if it's different again?

I understand the benefit of the filler line or cap before the pump ( return from radiator).

Good idea on having air bleed lines from the Rads High points - what size line and what size fitting did you use? I guess their the two tubes to the centre sides of the filler neck. 

George ( down under)