proportion obsession is silly anyway, if you want find out how the manga is, try reading it; instead bitching and complaining about the style an artist uses.
jajajaja... the art (or types of it) NEVER is proportionated. if you want reality, take a picture!!. think. have you ever, seen egyptian ancient art?,venus of willendorf? babylonian? even greek(if you need measure to get it, do it), or romanic. it is more atractive, and espectacular, exagerate. it's a conduct present even in animals... some teachers that I had, said the same shame shit. "that proportion is no real" or " the tit is not like that". only shame for they
Okay, these heads are too small for the bodies, yes. But the manga and anime are normally grossly out of proportion. Almost all the characters have near stick figure bodies unless they are giant blobs of flesh, so hard to bitch about anatomy being wrong in One Piece fanart, since One Piece doesn't care about it anyway.