Also, is it even needed to go with a double nut setup? They (the ebay store) claim that they are zero backlash. Based on what I've been reading on this site, this is most likely achieved by using slightly oversize ball bearings. Assuming this machine gets used quite regularly (maybe 700 hours a year), is this going to be considered a "wear" item?
Basically what I am getting at is "Should I design my machine for a double ball nut setup, or just use the single nut that gets supplied here: 1 anti backlash ballscrew RM2510-1200mm-C7 for CNC XYZ - eBay (item 250618180034 end time Apr-14-11 07:05:20 PDT)