LM8UU bushing for standard Prusa i3 y carriage with

Don't know why, but building my Prusa i3 (lasercut in nominally 6mm ply), after zip-tying the bearings into the Y-carriage, I found it bumped into, and was pushed up over the y motor at it's far end. Not much, maybe less than a millimetre, but that won't do.

The Y carriage is designed to have the LM8UUs zip-tied in and has holes 20mm apart to put the ties through and a slot to hold the bearing straight.

The other LM8UU bushings (such as the one this is based on) have wider spaced holes th