I added this mod to my Taz 5, and it's working out great. I immediately noticed that the x-axis motion is much smoother and requires less force. Previously there was always some play in the print head. Now there is no perceptible play at all. The first layer print thickness is now much more uniform across the width of the bed.
I would suggest that the specified length (436 mm) for the extrusion be considered a minimum value. On my printer that left about 5 mm of unused space (split between the end caps) . It was long enough to engage the t-nuts, so it all worked out. If I were doing it again I would cut the extrusion to 441 mm. That would exactly fill the available space.
This is an excellent mod for this printer. Next I will look at the Y-axis mod.
Parts were printed with ABS. I also used one of peircet's aluminum backplates.