Back up and restart from go.

Hand rotate the engine to half stroke, hold the cams in place. This makes all the pistons clear of the valves. Set the cams to the timing mark. One will be at the "bottom" of the varying valve induced cam rotation, and the other will be precariously balanced at the point of the cam lobe. I like to catch the crank sprocket by a quarter inch with a binder clip on the left side, go to the dside cam and catch the same quarter inch, careful to leave no slack, carefully catch the pointy rest cam paying special attention to the slack, slightly rotating the cam with a wrench to perfectly align the belt, then catch the tensioner preset alignment, hand holding out any slack. I then tap the belt on sprocket by sprocket with a light soft face hammer going around the circle. Release the tensioner and hand rotate the engine two complete cycles to test for any interference and to check that all realigns each rotation.