You stated the most common mistake, gap at the top, lower the back....wrong, RAISE the front 99.9% of the time. But lets back up. Think aligne the motor to the shaft, not shaft to motor, always start with the shaft is the correct position with good strut bearings. I have reviewed the available youtube videos on this subject and have yet to find a practical one. Producing a decent video is on my list for this coming off season. My wife said I need a cute female assistant to do this with, nobody wants to see me in the bilge, the search is on for the right person.