what I meant was that if a ppl is taught critical angle occurs at an air speed of about 55kts he can know that in a 60 aob turn at 2g stall speed will be about 80kts
He doesn't really need to know that the critical angle, there are no visual cues and stalls under g will be sharper so less warning from the airframe.
In this instance best to know not get to close to 80kt, unless he wants to do max rate/min radius turn and hold it on the buffet.
sure shaggy but in GA weight variation is generally so small it makes bugger all difference, so as far as I can see speed is a useful reference point as long as you accept its not definitive.