As long as the end of the overflow tube is below the surface of the liquid in the reservoir, the vacuum created in the cooling system as the engine cools down should siphon the coolant back in. Make sure the catch can is located near the top of the radiator to minimize the amount of lift the return has to make. Also be sure the radiator cap makes a good seal on the filler neck.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!