Just done another sketch to show what I mean about allowing the bow to twist when it is dropped to line up with your target/chrono...I expect you'd worked it out anyway.
It shows the aim line and centre-line being two different things.
It also shows the potential problem of the string hitting the track if the bow is too low.
With the your previous test when the bow was mounted high to give "correct" alignment... the whole machine then needed tilting down to get the aim line right to hit the target square on and not at an angle.....
I think you just gotta mess around until it does what you want
I think I've been too clever for my own good... can't stop postint (hic)... too much red wine with my dinner!
Del