Hey hey,
today I was flying with my elytra and with the help of my punch 2 bow, I managed to get up to 700 blocks above bedrock.
It should be possible to get higher, the only limitation is the durability of the bow or the elytra.
So I now officially claim to keep the height record on CraftyMynes. You think you can beat it? Well try it and post a screen to prove you beat me or the latest record keeper.
Good luck!

btw you cant see the bow in my hand since I used F5 but I cant even see myself because of the imense height, what makes the flying a bit more difficult.