Large Bosses

So how do I go about making large bosses like in the mythicmobs video, already tried making a type giant mob disguised with a player skin. But of course skin doesn't resize to giant and makes a regular mob sized boss. Any way to use a skin url instead of a player name?

On another note how to get rid of health tag under mob name type player example:
Disguise:
Type: player
Skin: 'FoidzaFlow'
Player: '&aCrazed Fighter'

How it looks ingame:
Crazed Fighter
0% Health

Thanks!