I know of two instances (both in Supercubs, after a loud bang and loss of power) where they successfully 180'd and landed, and both were at less than the recommended 500ft (land-ahead) height when they lost power. Both pilots were very experienced instructors, and knew (in hindsight, from what everybody is taught) that at that altitude they shouldn't have attempted such a maneuver, but it felt right at the time, and ended up with a safe outcome.
The FAA has some kind of graphical demonstration in their textbooks, showing that if you make a standard turn you end up 800' under the runway after doing a 180 below 500ft, or words/pictures to that effect. As a student pilot, they don't want you to have any idea that such a turn might be possible, and quite rightly, as the statistics show that this has led to a lot of accidents in the past. So, statistically it's safer not to try it, and that's why the FAA preach it that way. They don't like the idea of low altitude stall/spin accidents.
A quick google gave this
http://jeremy.zawodny.com/flying/turnback.pdf (which hopefully closely answers your question) and there were loads of other results which may explain your answer, so have a very good look there as it seems like a rather in-depth study from a reputable source.
I think John Farley has done a piece on this somewhere (which I recall reading in Flyer mag a while ago), and mention of that is probably elsewhere on this site, as I'm sure it's been covered before, but I don't want to be the smart-ass pointing it out to you, and can't be bothered looking right now.
The only studies I know of, are the FAA's and the link I've given you, which I've only just found and haven't finished perusing yet, due to the off-putting formulae within the first few pages! I know of similar "studies" regarding canyon turns, and all the comparisons of rate/radius at different speeds with different flap settings, slipping/skidding turns and all kinds of weird and wonderful things, so that might be of value.
You could always try it yourself, at a safe height, but it sounds like you really want to get technical with it, so there would far be too many variables involved to satisfy such a need for perfection.
I'd say that it's definitely possible from the right altitude, and I'd hedge my bets that we'd all probably be surprised that this "magic altitude" for any particular SEP, on any particular day would be significantly lower than 500ft AGL.