Hi - all fantastic info - you're a star...Yep, stack height can be reduced
is typically 1.6mm Al around 6-8 mm long
Divider doesn't need to be totally sealed,
a little seapage past the divider is of no consequence.
Not sure I quite understand you here - I have done a sketch of the current layout here:If there's room a 'full flow' header tank is a good idea. Rad top bleed goes into header near the top, header tank has an outlet in the bottom which is spliced into the bottom hose before the waterpump- the system should then self bleed (engines with built in 'steam traps' aside)
http://www.maplesigns.co.uk/temp/cooling.gif
The system is filled through the pressure cap tank (very small tank) - and the rad is bled at the same time - then closed off.
The engine also has a bleed on the cyl head at it's highest point.
Thanks for all your help...