After dealing with inconsistencies and backlash with the belt drive design, we decided to give the lead screw a try. We've started with the Y-axis for the trial. So far so good!
UPDATE! Our matching X-Axis lead screw upgrade is now available here!!!

Along with the motor and bearing mounts, we also lifted the bead with an altered frame foot design. Please note that to keep all dimensions consistent and for this upgrade to be functional, one must utilize the new taller frame feet. Naturally, these are designed around the 8mm rod frame build.

Source files now available in Thing Files.

Notes:

• Bearing mounts must be printed with supports, easy to generate and clean up.

• Base printed in PLA, lead-screw components printed in ABS.

• CREDIT: Y-EndStop from ePoxi's Mechanical Y-EndStop holder for Prusa i3 here. Great file!

Updates:

• Jan.12, 2015...Uploaded improved plate-follower coupler bracket.STL (added ribs for extra rigidity)

• Jan.12, 2015...Uploaded bed cable guide.STL as an option. Easily mounts onto the Nema 17 with zip ties. Prevents cable bundle from snagging.

• Jan.18, 2015...Uploaded ePoxi.i3.Y-Endstop.BetterHalfMod.STL that we are currently using. Solid end-stop design, highly recommend.

• Jan.21...Added YouTube video printing a test object.

• Mar. 28, 2015...added Inventor files (.ipt) to download list.

YouTube Video:

Here is the printer in action

For a closer look of the finished print (untouched): short imgur album

Test print is the Deprime test object found here on thingiverse

Running Repetier Host V1.0.6 and Slic3r V1.1.7
Natural ABS
.15mm first layer .2mm for the rest
30% first layer speed
45mm/sec perimeters, 70% outer perimeters
60mm/sec infill, 40mm/sec top layer infill
80mm/sec travel
25% honeycomb infill (just to show rapid changes in direction)

Higher print speeds are possible but, so far, this seems to be the best balance for quality.

Check the Instructions tab for parts list and other important information regarding set-up.