Conversion of Momus to ball screw for X and Y

Hi All,
Been away a long while but built my Momus about 4 years back and it has done some useful work BUT has on occasion missed a beat on y axis travel and reluctantly after lots of tweeking have concluded that it is the cog belt drive on Y that has been the culprit. So I am considering retrofitting with 16 or 20 mm ball screws (x2).(20 mm might be overkill).
Has anyone done this exercise I wonder.
With respect to using the Gecko controller to drtive TWO outputs to Y steppers on the possible ballscrew upgrade I understand that is possibly ok but total current for both is limited to 3 amp. Again any comments . I am not sure if the standard Gecko off hand has a 4th driver which woulkd solve the problem as I have no interest right now in any other 4th output.
Any comments appreciated. Work is primarily thin ply MDF acrylics.
Raynor