you really should loosen all of them if you are going to be aligning the clutches. Do you have an adjustable engine torque stop? Definately worth the money, keeps the alignment and center to center in check much better. If you don't have one, I usually set them up with a little bit longer center to center than recommended, along with the engine turned slightly clockwise from perfect alignment with the idea that under hard acceleration, the play in the rubber mounts will pull the engine into close to perfect alignment and center to center. Little tricks you learn along the way, but a torque stop takes out the guesswork.