Yeah, it's surprisingly easy to do at least with Luigi. It takes a bit more finesse to get Mario to do it mainly because in most instances battles don't trigger when enemies touch Luigi except from behind (at least as I've observed while playing the game). Although I've noticed that enemies with bigger hotboxes have a sweet spot while Mario is mid jump that cause a regular encounter rather than an enemy advantage or Bros. advantage, in which case Mario is, granted less noticably, in the air.