my comment would be to use two check heights so you can verify the g/s.
the dme distance that you capture the slope.
ie. 3000ft approx 9.2 DME (all depending on the approach plate, I used AA ILS/DME 23L)
and then another height along the way. this will verify the slope.
by using two heights the error is reduced and is a straight line to compare.
hope this helps.