So it's a bit unorthodox and I wasn't gonna post it as I'm usually shut down around here when I ask unorthodox questions. . .but I saw Roy Nelson do it in a fight I was just watching so I'll go for it anyway. So my reasoning is you can use the fact that you're often off balanced after swinging an overhand by going with it and throwing a backfist, effectively exploiting a fairly compromising position before your enemy can. It can be a spinning backfist or a regular one. Here's a video of the fight I'm talking about, skip to 12:45. I know Nelson's not the most technical fighter but I hope we can build on this with stuff like proper form, defensive considerations when throwing these, and footwork/positioning ideas.