That doesn't seem to be the right question.

If
moving the arm down gives improvement, you get signals from higher above, so the solution for that would be to
adjust the dish UP !
No the arm down or up wasnt making a difference. It was the lnb itself facing more downward was raising signal a few points higher but there is no way to keep it in that position.
Or you might want to check if the LNB position matches the offset angle of the dish, so to check if the arm might be constructed in too high a position?
"Easy" formula to check that (for flat, paraboloid dishes), to see how long your topstring should be, is:
Topstring = Bottomstring + squareroot ( (dish-hight squared) - (dish-width squared) )
Where topstring is distance from top of dish to focal point (phase center of LNB feedhorn), and bottomstring the bottom-variant of that.
Of course you could also check the distance from LNB to dish, but then you'd need a more extensive calculator/calculation.
Well, the problem is that when adjusting one variable at the motor setup to get improvement on a certain satellite position, usually means that another variable has also to be adjusted, to keep following the arc.
Have you used the 'modified motor angles' for setting up your motor? (E.g. this table:
Elevation / declination chart )
Greetz,
A33