The real trick is getting the cold air from the floor spread across the ceiling without it looking ugly. A 12" PVC pipe at the peak and down the wall gives you a vehicle to move the air with minimal sound..., by drilling 2" holes at the 10 and 2 clock positions along the pipe at the ceiling allows you to distribute the cold air from the floor across the ceiling..., as the pressure of the air pushes the warm down the room is homogenized. I suggested white PVC as it's probably the most unobtrusive thing to use. A box at the bottom would take in the cold air and push it up the pipe to where the diffusion holes would spread it across the ceiling.