I've just bought a case of Abena M4's, which is a diaper I'm pretty familiar with. It would appear that they have been manufactured wrong and the tapes have been put on the front. The reason I think this is that the tapes are on the shallower wings which normally go at the front, this makes it tricky to get a good fit. The other problem that you notice once they are on is that the thicker padding is at the rear and up front you only have a thin layer with the thick stuff starting in the crotch.
Has anyone else noticed this with a recent case of M4's? I've sent an email to the supplier, we'll see what they say.