You can wedge-fit slip fit eyes, but they tend to require front-to-back spread to the handle in addition to side-to-side, so a cross wedge or dowel wedge can be handy, and they can be more finicky to get a smooth shoulder on than a wedge-fit eye because the bottom of the eye isn't at all tapered. In countries like Spain, Italy, France, etc. that use slip-fit eyes, one often finds such axes outfitted with wedged handles, as a matter of preference one way or the other.