Render your movies to 2048 x 768 or somewhat more narrow, as your overlapped picture will be a bit smaller. I´ve found it quite easy to use corner pinning in the mixes when setting up two beamers, and the Catalyst will do the blending nicely. You might want to adjust the gamma on the ramps a bit to make the blending all seamless...

It´s easier than you´d think, and I´ve been surprised by how good it looks, even on quite big areas of overlap.