It's funny, in Bara, they don't have such hard core designations of top or bottom. There's none of this bickering over who does what (from all the ones I've read). But then again, Bara is more realistic than yaoi because actual gay/ bi men are writing them. Yaoi is female fantasy after all. The uke is the stand in for the woman, so reversing isn't really possible (because women can't reverse, right?).