Nice design! Did you ask the machine shop to press fit the bearings in for you? How did you install them? Any updates on your project so far? Also, do you separate your aluminum parts with washers?
Are there bearings at the interface between the support block and the 2 main bars? (I have included an image in the attachments; the areas I am referring to are indicated by the blue arrows)
Are you using a washer there? Does it adequately eliminate most friction?