Agree with Stik about breakoff height. I have often thought there should be an exception to the low flying rules to allow PFLs down to very low levels. Quite how this would be policed so it wouldn't become a 'beat-up merchants' charter I'm not sure.
I break off above 500 feet to (hopefully) ensure no-one accuses me of low flying. But I realise the resulting PFL is not that useful, but better than not practising at all.
I also do them at the airfield right to the ground, traffic permitting - but that's not so 'real' since its bigger than the average field and I know all the ground clues.
SSD