Flying for fun.
With your lecture hopefully over from Beagle may I say I totally understand where your coming from.
Both of us treat the spin with respect which is why you have posted this topic to find out more from the guys who have pushed the boundarys.
I too want to become much more aware of the envelope so your better equiped to deal with a problem (if aeros is your thing).
The RAF in general know surprisingly little about flat spins and do not address it in training. The statement that you should only practise spinning via the POH is absolutley sensible however when are you ever going to inadvertenly enter a spin in POH approved manner !!!
The Airforce always taught the 'incipient spin recovery' (centralise controls) which worked for any attitude as long as you hadnt fully entered a spin. I always wondered what if the aircraft did go flat ? I was never taught what to do if this happened ! Maybe because it wouldnt happen as long as I entered in an approved fashion !!!!!!!!!!!!!!!
There are lots of books/videos out there. Daroll Stintons books contain some really in depth Test pilot stuff on spining but I too have found it a struggle to get good gen on flat spins. As many aerobatic books and videos are a good start, it may also be worth trying to get yourself a one off flight in something that is fully appproved to do it such as the Yak 52 with a russian QFI if they are still here.
If you do get some really good flat spin material could you please pass it on.