Well my thoughts are....
Turnbacks are safe given an appropriate amount of height.
You *must* pull to the nibble of the stall in order to get the max rate from the turn. Anything less is wasting distance in the turn...most raf chaps will be familiar with buffet flying - if you arent get a suitable qualified instructor to show you this...aerobatic instructors are a good bet here...
The calculations for stall speed in the turn that a lot of people quote are flawed - almost all stall speed in the turn calcs rely on maintaining level flight...
Basic instruction behind not turning back is IMHO correct. The point is that there is NO decision to make...the last thing you want is someone um'ing and er'ing about whether or not to turn back...if the basic response is EFATO then they are more likely to survive...incidentally if you have enough time to think about this having set up the EFATO then you are getting close to a safe enough height - if you dont have time to think you are too low for turnback...
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Must say I am curious now about say 60-70deg bank + pull to buffet - to see how much height a pa28 would actually lose - could come in handy one day...next time im on my own I will give it a try and see what happens (safe height first obviously + HASELL just too make sure I dont meet anyone else in case I get it wrong!)
Interesting...