I'm trying to design a dungeon competition in a game and I feel like mephits would fit perfectly for a group of 5 level 3 PCs. Only up to a couple per room should fit perfectly, the players are a diverse enough group. However, I don't want them to have flying. Ignoring the summon ability (I'm only using that for a couple rooms to surprise the players) would there be any change to a Mephit's CR? I'm thinking it would drop it a point, flying is a big deal at low levels.