MendelMax Z-rod lower mount - AlephObjects deriviative for thrust bearings

I am one of the unfortunates whose original-style z-rod lowers both delaminted at original assembly time. I repaired them, and they have been fine, but it has been in the back of my head to work up a re-design... then AO released : http://www.thingiverse.com/thing:15861
This piece incorporates everything I had in mind... except that Thing was designed to use 608 bearings. I have the "original" thrust bearings for z-motor load reduction, so I derived this version implementing the hole sizes