Okay now i understand that you mean actually jumping onto a hitbox and then outside of the map area, the problem is that in single player you aren't kicked for floating, there isn't another way to get around this except to make all hitboxes either tiny or huge
It's not for singleplayer, i'm making a recreation of Kanto in multiplayer with my build/dev team.
These hitboxes, what are their purpose if i may ask? Are these hitboxes only for throwing the pokeballs at them? If so, why not change that mechanic?
I really have hard times hitting pidgeys/spearows/rattata's (because they're so small!) with my pokeball(s). Why not, if a pokeball lands, check for an pixelmon in a radius of 1.5 blocks. And if there's a pixelmon, or more, grab the nearest one to battle with?