Height of radeator overflow tank

[forestb]

I have heard that the overflow tank has to be the same height as the radeator. Does that mean the two caps should be at the same height? How much wiggle room do I have with that?

[vince1]

I think the tank I put in my car is a bit lower. I don't think it matters. The car cools off and the fluid is sucked back into the rad.

[markeb01]

It seems to me they do like being higher up. When the overflow is within an inch or two of the radiator cap, the radiator stays full. When the overflow is half way down the radiator, there will be up to 1/4" or greater gap under the bottom of the radiator cap before you reach the coolant.