DIY Marble - Metal Machining 3 axis CNC Router

After pippin recommendation I changed X axis design.
After changing double linear on each X axis to one linear rail, mass of bed frame and bridge are changed.
Double linear rail type : RGW35CC - 35 mm width rail - 100 mm width linear carriage block
One linear rail type : RGW45CC - 45 mm width rail - 100 mm width linear carriage block

6 linear carriage bearings canceled, 2 piece of 4m length linear rail canceled.
With the reduction of steel profiles, there is approximately total 1.500 - 2.000 USD cost reduction due to one rail design.

Old Mass :

Bridge : 1.200 kg
Bed Frame : 4.800 kg

New Mass :

Bridge : 1.100 kg
Bed Frame : 3.950 kg

I need help about X axis drive. I think both X axis and Z axis should be rack&pinion design instead of ball screw.
At X axis ball screw is way above linear rail I didnt like it, and rack&inion will get the ram closer to the saddle for Z axis.
Any ideas.