Prototype carriages for regular extruded aluminum (ie, not v-slot) using straight wheels (http://www.framingtech.com/c3/c75/c103/29mm-Diameter-Roller-Wheel-for-6mm-Slot-p490.html )
Nice, Chris. So, what’re you up to?!? 
Large printer (currently a cube 1/2 meter per side, but likely to get smaller). I’ll post pictures when there is more to show. I don’t know if any of the new stuff I’m trying will work, but it will be an interesting experiment.