From what I could see it would have been possible to mount each extruder with 2 LMxUU bearings. This might reduce drag on drive motor a lot. Might even reduce it fair enough that you don't have to run it has high.
If nosy is the reason for not choosing LMxUU bearing. Then it would be a good idea to compare the bearing used against http://www.thingiverse.com/thing:24990 and http://www.thingiverse.com/thing:24990 for drag. Both of these printed bearings hold oil very well. The big advantage is these bearing are long they spread the twisting force along the bar more so less indvidual bearing less jamming between bearings due to twisting. Yes you can have a set of metal LMxUU sitting in case one develops a issue to print replacement.
http://www.igus.co.uk/wpck/default.aspx?Pagename=DryLin__R__RJMP&C=GB&L=en Also exsit for those who don't have printers.
Basically LMxUU bearing mounts take many bearings. Some are more low drag than others. Some are more nosy than others. The printed and the plastic ones are very low noise.