Best Linear rail mounting set up

[j2sip]

Please help me choose which of these mounting positions is better. This is for a woodrouting 1200mm x 900mm x 120mm CNC.

36"(900mm) length
20mm THK Linear rails and trucks
1/2"-8 4 start Roton Acme screw
(1) 425 oz-in HobbyCNC Motors(3NM)
Luc's THB6064AH driver http://www.ecomorder.com/techref/ecomprice.asp?p=416074
44v Power supply


6"(150mm) Channel bar which allows the rails to be mounted at a good 112mm apart. Very heavy. The gantry will weigh close to 80lbs(37kg). Which brings me to another question - will the above single(stepper)/drive combo move this heavy gantry reasonably?


This is a 4"(100mm) channel bar with the rails positioned as shown. If I mount them(rails) like in the 6" channel bar, a mere 56mm separates them. 10 to 12lbs lighter that the first.

Thank you in advance for your answers.

Jordan