Why not get the student to look at the requirement that never changes i.e. the requirement to cross the threshold in the landing configuration (the one prescribed by the flight manual) and the correct speed from a stabilised approach towards the correct aiming point.
If that is acheived then there is a good chance that the performance fingures published by the manufacturer will give atleast a clue as to the landing distance required. If one does not do the above then no point in even looing at the performance figures - they are meaningless.
There are 101 ways of acheiving that correct threshold crossing.
However, if we add in some workload management and the requirement for lots of quality lookout at all times then the configuration changes will naturally fall into a patern that has nothing to do with square, oval, bomber or microlight circuits but with time to the threshold.
Having got away from the pattern then the pilot can simply configure the aircraft in stages in good time for a safe landing...be it from an approach with power, a practice glide or even a forced landing.
Smooth unrushed configuration changes during the approach to land need to happen in sufiient time to have the aircraft stabilised by one's minimum height to be stabilised by....most light aircraft operators use 200ft unless it is an emergency. i.e. if not fully configured and on target speed at 200ft then go arround.
The whole idea of do this at that position in the circuit will only really work fully if there is no other way of making an approach which avoids that place in the circuit.
Related example - where do you put the gear down? How many would say at the downwind position? but what if you are on a straight-in? where is the trigger there?
How about you put the gear down at 4nm from touchdown. Now there is a fixed point that no matter how you approach the circuit you simply have to pass. Of course the 4nm from touchdown point in the standard circuit is somewhere about the downwind position and of course this leads nicely into the CAA guidance of aircraft in the circuit at downwind (about 4nm from touchdown) compared to a flight on a straight-in approach calling long final - more than 4nm from touchdown.
Thus when it comes to flap then there is simply the requirement to have landing flap selected, the aircraft trimmed and the approach stable by the decision height.
You must put the flaps out on base works great until.....slightly tighter circuit requested by ATC, tailwind on base, chop the power.....DOH Carbheat (too little time for the period of heat before changing power), must start down, shove the nose down, DOH, need to slow for flaps, where is the runway DOH we are on the centerline, bank and pull it round, DOH we are high, DOH DOH DOH........Did I mention lookout up final? NO!!!
Perhaps better to think OK we are going to be a little tighter in this circuit so we are closer to crossing the threshold than expected so we need to start the configuration changes (and perhaps descent) here at 2nm to go (on late downwind in this case).
How many instructors get their VFR students to relate their position in the circuit to distance from touchdown? One can talk all night about lift drag ratios and excess thrust but if it is a bomber circuit, a tight slipping oval spitfire arrival or a forced landing into some farmer's field.....it allcomes down to judgement as to how far to go to the "threshold".
Regards,
DFC