Timing Belt Design

[3Dsigns]

My hotwire foam cutter machine is a little over 10' long and I intend to move the x axis uprights with a timing belt on each side.

The timing belt I bought is 3/8"wide and steel reinforced.

If I mount a stepper motor at one end, run the timing belt i a continuous loop, attaching both ends to the upright, I'm concerned about backlash from the longer belt. But if I mounted the motor to the upright, looping the belt around the timing pulley and an idler pulley, I'm thinking it could be too much extra weight.
How would you do it? The timing belt and stepper motor are in green. Thanks

[3Dsigns]

This is the frame with the x axis uprights attached.

[foobillious]

I'd mount the motor at one end of the base, pulley at the other and a tensioner/idler pulley on the gantry.

[3Dsigns]

Thanks!