hmmm...good point, i was thinking about negative effects on the stem, not the bars. i only ever did this quite some time ago with a mtb stem that had track drops on it, then a pair of bullhorns, but both seemed fine. since then, i've only used flats and risers...but iirc, i put both the track drops and horns in a 26.0 stem with no problem after running them on a 25.4 stem.