In the Mix Options window of the HUD select the mix, and adjust the offset. For example and offset of 0.75 will shift the mix relative to the object by 75% to the right. Conversely -0.75 will shift the mix to the left. The amount of 0.75 corresponds to a blend amount of 25%. This is a simple concept on two screen blends. When it comes to larger numbers of projectors and mixes though, just use the math to calculate the shift offset based on the edge blend.