Another useful Tip if you are trying to get good crowns on monsters is to use tools that show Things like Monster HP and Size.
I am using the tool "Smart Hunter" and it shows me if an monster has a crows, it's Hit-points and the Hp of it's body parts as well as other useful things like player damage on an monster.
As far as I know those helping Tools are not forbidden to use, since they do not alter your account and I have never gotten any negative feedback about them so far.
What I do when I am looking for a specific crown is: I enter a quest, regardless if it's an exploration or one of those event quests and look if the monster in it has any gold crown size. This saves me a lot of time, since I can easily sort out quest with monsters that don't have the right size. (since doing the same exploration twice gives you a monster with the same size)