My Shapeoko2 is now a current spec x carve. I put on all the upgrades including an aftermarket Z axis from cnc4newbies…what a difference. I’d suggest stiffeners, 9mm belts/pulleys, and a new z axis at a minimum. The X controller is a nice addition as well as the new x axis carriage and extrusion. All these things tighten it up quite well.
If you dislike videos see the 3rd post here for a written recipe.
Calibrating my X-carve 1000 - X-Carve - Inventables Community Forum