I'm no expert so maybe I'm not getting it but I believe your problem is you have slack on both sides of your belt when you're releasing the tensioner. You should line up all 3 marks, run your belt across both cams and under the top pulley with no slack. Then put it around your water pump and the crank again still with no slack. The belt should line up with the notches on the crank pulley. So from your left cam sprocket (looking at the front of the motor from in front of the motor), under the idler pulley, around the right cam sprocket, around the water pump and finally around the crank there should be no slack. All slack should be on the tensioner side between the left cam (again standing in front of the motor) to the crank. Slowly release the tensioner and viola!! Everything should be hunky dory.