Interesting reading guys.
Maybe a bit late in discussion now but I see turnbacks relatively frequently, perhaps more than some and know the procedure well enough.
The ones that I do see are usually carried out by aircraft that have height (500- 800ft AGL min) and the speed to complete the turning component of the manoeuvre. These aircraft are HPAs and would probably be able to complete a turnback at a lower height but those aren't practiced so I've never seen one.
Would I do it in the clubs 172? Most unlikely, there may be that one time when... Another of aviations great 'ifs'. All credit to those who have their own aeroplanes and have practiced turnbacks and can explain all the theory behind doing them.
Cheers
GW