I have been running all my effects and such in vid-gpu, and right before sending to the projectors.. using 'texture to video'
the vid-cpu stream can then be linked to different stage projectors. there is a cpu hit in converting texture to video.. but I have found that its much less that what I gain from the GPU pipeline in effect processing etc... I can maintain 30fps in my setups. It might be a solution for you. Just do as much with the GPU as possible.