In my opinon, both personal and profesional, the Darkflight should be on the front, and AM on the flipside as you say. cover on the back is not a good idea for many reasons. First of all no one ever does it that way, so it will only look like a backside. Originally, I wanted just ONE cover for both bands, and you probably understand now, that would save everyone for much trouble. Of course I understand that each band wants their own cover, but this is after all split, and not to releases packed in one "special price"-edition. Most split 7" at least have just one cover.
Anyway. When it is like this, I think DF should be on the cover for several reason. First and foremost because the cover is a cover people will notice in the shelvs because of the strong colours, and just because its a good cover. I don't say that AM will be worse in any way, but less commercial somehow..hope that makes some sense. Sorry if im sounding negative..hehe.