I'm trying to settle on a design, but I was advised to try all 3.  The 3 designs are 1. round linear bearing (current) 2. Y- Linear bearing 3. U Groove wheels.  Im almost ready to print a u groove wheel for a 1/2 emt, and 5x16x5 bearings.  I found 8 x 16 x 5 are also cheap bearings that should be suitable for the Y linear bearing.