G'day Alex
The horizontal base of the wedge should be as close to perfect level as possible. (use spirit level on 2D axis)
Then You would want the tilt plate angle to be around 33° degrees,
for your (Sydney) location. So the physical tilt angle would be 57 degrees.
(i.e. 90° vertical - 33° Sydney = 57° plate angle)

Use a protractor on the tilt plate and a bob string line.
Make a paper scale with this 33° in the middle.(also scribe mark the wedge)
Adjust the tilt plate up and down (knob on rear) to other positions and mark on paper.
Then transcribe details onto a thin Alu. strip painted (from drink can) and glue into place.
Exact fine tuning is done via drift aligning