Hi,
just want to put my 2p's worth
reading a few posts here stating facts & figures of when to do things - 1 particular thing I have seen in experience, is a student grabbing hold with extreme vigor, the idea that you turn base2final at a PARTICULAR height.
whilst in practice this works out ok - it all goes horribly wrong when they are then asked to position for a 2 or 3 mile final - they still aim to turn final at 600ft - completely ignoring that the approach has LOOKED low for some time.
i cant argue on the When to turn, when to call, how wide/close, since this is done with reference to the strip & not the instruments - nor do i advocate learning the local circuit with reference to ground markers - houses/villages etc
I have found that if students learn the "overall circuit 'picture'" they find it easier to transpose that when off visiting different airfields
Less is more, perhaps, in this case & rather than fixate of precise numbers (with the exception of AirSpeed), learn what it should look like and fly it!
..2p spent!
BB