Some possible problems with this layout are:

• Will there be enough coolant flow to keep the radiator hot?
• Will this work in a zero pressure environment, or will the expansion tank tend to overflow?

For the connection to the expansion tank and from the heater, I used the hoses that were plumbed for the heater. They are 1/2" I.D. hoses.

Here is an image showing the overall design of the cooling system.