This is a fairly basic carriage, based on an old printable linear rail design. It's not complicated to make, and the tolerances are quite low, given the age of the design. It serves as a base component in a motion system I've been working on.
It really doesn't matter what settings you use. I'd recommend doing a decent number of perimeters, though, as you need to thread screws into the plastic, but otherwise it's up to you and what your printer can do.
Building the carriage
After printing, place an M8 nut into the eccentric nut trap, put 608ZZ bearings on three M8 screws, add an M8 nut on top of each of the bearings, and put the three screws into the side opposite the eccentric nut. After tightening the screws down, add an M3 nut to the trapped nut mount inside the trap, and screw an M3 screw through it to hold the nut in place.