Hi,
I don't believe two motors may help.
First, a single motor is pretty enough for that task.
Possibles issues and solutions :
_ flexible belt => replace with quality fiberglass armoured belt.
_ wobble => replace your loose LM8UU by polymer or bronze bushings, and tight them for a no clearance fit.
_ not so round idler pulleys/bad belt guidance => replace idler bearings by proper GT2 pulleys mounted between 2x625RS bearings on custom Xend with flanges.
++JM
Edited 1 time(s). Last edit at 09/13/2015 04:44PM by J-Max.