I am sure somebody is going to have a go at me for saying this, and I don't wish to start yet another "why do some people fly such big circuits" thread, but isn't there a slight contradiction between safety (careful and correct airspeed maintenance around the circuit) and flying the tightest possible circuit?
I fly a TB20, so by the end of the downwind leg I want to be trimmed at 90kt. Sometimes I have arrived quicker but I make sure I am trimmed to 90kt on the base leg. I verify this trim position with hands off the yoke.
The gear (and 10deg flaps) goes down on the DW leg, and unless descent is desired the MP goes up to 20" to maintain the power over the extra drag.
So the base to final turn is done at 90kt. The stall speed in this config is 70kt (at MTOW, 30deg bank) and 1.3 times that is 91kt which makes 90kt quite reasonable (Vref = Vs * 1.3) for a safe turn. Even safer if the turn is descending, with a slight vertical acceleration during the turn (unloads the wing).
Then landing flap, and speed drops to 80kt. No more 30deg turns now (one hopes) so we have 59x1.3=76.7 which is fine for a Vref of 80kt.
I do the base turn at the proper place for the published circuit, only to find some other pilot cut me up on the inside, having flown a much tighter circuit. OK, in a C150 you can fly a tighter circuit, but not that much tighter. Usually they mis-judge it and I have to go around. Sometimes several times (e.g. Sunday, Stapleford).
Occasionally, it's obvious that there is an instructor on board, so the student is doing this on his orders.
To me, it's patently obvious that at least some poor sods are not taught proper speed management. They are taught to fly a "proper airmanship, young man" tight circuit, which the instructor obviously knows how to do, having been doing it for the last few years. But the student won't know the effect of G (i.e. the combination of the effect of bank angle and vertical acceleration, etc) on the stall speed. Most likely, he won't have a clue what the stall speed is for the various configurations - I never knew this in my PPL training. One should not be flying max-performance tight circuits, say 10kt above level-flight Vs, at this level of training.
I could fly DW a bit slower, with full landing flap which gives a safe speed of 63 x 1.3 = 82kt (or so, the power setting will have quite an effect too) but why should I fly around with a plane which now has a sluggish control response, just to skim off 8kt? The margin for turbulence is now pretty thin and I still have two turns to make, or one longer one if flying an oval circuit which a lot of people don't like.
One can make the same case for any combination of the many types found in GA. Pick any two with a 20-30% difference in Vs, and the slower one will be tempted to cut up on the inside.
People should be taught to fly the proper speeds, and they should be taught to follow the person in front, not to try to save about 50p in fuel by cutting up the person in front.