possible issue with getting top mob resulting in inaccurate display name jockies. Could do get recusrive passengers and then check y height and highest y level wins if is = then it just get's overridden from the previous iteration.

Current logic get current passenger at 0 until finds top

I don't think there is a way to solve this since comparing y levels won't do and there is no defined top

Well I guess comparing y levels is alot more likely to succeed then to simply not try at all.

The issue is this might lag up servers creating all those entities I will check the ms count of a huge stack if I don't like it then we are doing it via 0 passenger and no new 1.9 support

Even if I get the top mob in entity form there is no way to identify it back inside of the itemstack's nbt I could do based on most count in the stack but, that's not a garentee anyways.

unfixable the way the game is currently designed for spawners