No, the return needs to be at the top if possible, otherwise the turbo may fill with steam or just hold air in the pocket. I guess it depends on the setup though and how hard it's driven.
Just think of what would happen at the track, the turbo is red hot and will be for a while as you pull back in. The water is barely flowing at idle and if you turn the engine off there is no flow. In this case the water will turn to steam and it needs to go somewhere. It needs to get to the radiator cap to be purged from the system.
The steam and hot water can create water flow if done right using convection to cool the turbo better.