Help! Need to use 2 pieces Blackout Cloth

Since my screen is going to be roughly 8' high by 14' long I bought two pieces of 54" wide BOC. I am looking for advice on how to put the two together and minimize the seam. This is for my outdoor theater application. I am also looking for advice on how to hang this on or over my garage door. Thanks in advance for any information you can give me.