Initially, I just shortened the x-rods so that the z-rods were touching the table, and just slid against it. This fixed the wandering but introduced friction and was a terrible solution. Eventually I attached one side of the Y to a linear rail and this completely fixed the wandering and the friction - this is essentially what the LR3 does too so it might be worth upgrading as the LR3 fixes many of the other quirks as well.
There are some pics of my LR2 Y-plates attaching to the linear rail in this thread