Elytras will lose their glide functionality with smart moving installed. Smart render also butchers the flight/gliding animation.

I'm going to try and hack together a work around, if I manage it I'll make a merge request, but honestly a lot of this mod is outside of my ability to code.

EDIT(2): I've fixed the mechanical half of the problem (see pull request). My previous assertion of collisions being messed up was incorrect, after further testing I've determined my fix is a 1-1 from vanilla (again on the mechanical side alone) all that remains is to fix the rendering issue, something I'm somewhat close to solving after some additional poking and prodding. It's unlikely, but the render half may require a patch to the companion mods as well (api and render)