If I am reading your post correctly, what you are seeing is NORMAL.
The rotor will stop at a point AHEAD of the #1 HT terminal, "til the impulse trips, then pass the terminal at the instant the points open/spark occurs.
If you actually have lined up the correct timing marks, you have done your job, and all is well.
(Copy and paste this link for the factory Blue Ribbon Mag Manual, if you do not already have it.)
http://www.cleancomputes.com/Cub/Blue%20Ribbon%20Service%20Manuals/GSS-5035%20Service%20Manual%20Magnetos/index.html
The rotor will stop at a point AHEAD of the #1 HT terminal, "til the impulse trips, then pass the terminal at the instant the points open/spark occurs.
If you actually have lined up the correct timing marks, you have done your job, and all is well.
(Copy and paste this link for the factory Blue Ribbon Mag Manual, if you do not already have it.)
http://www.cleancomputes.com/Cub/Blue%20Ribbon%20Service%20Manuals/GSS-5035%20Service%20Manual%20Magnetos/index.html