Jaycee,
I've just noticed (in your 'bench' photo) some faint impressed numbers above the dish/motor mount. They appear to state, 20, 40, 60. I'd hazard a guess at those being your elevation markers. So, I'd turn the mount back the way you had it at first and look for some datum line on the mount you could line up with those numbers. If you find a marker line try setting the dish at quarter the way from 20 to 40. If there isn't a mark on there, I really don't know what you could use on the mount as a reference point for the elevation markers. Anyone else with a bright idea? (Apart from a rough guesstimate of course!)