The launch feature (holding crouch on top of a campfire) doesn't work with other mod's elytra-type items. Specifically, Alex's Mobs tarantula hawk elytra and Enigmatic Legacy's majestic elytra don't seem to work. There is a forge:elytra item tag; maybe it's possible to use that (for forge at least)? Though, I'm not a java programmer so I don't know how difficult that would be.