CarveOne,
It looks like you have a good handle on the bearing adjustment, but here's a quick trick. Since you have to loosen the bearing bolts in between each adjustment, it's good to get things close without the lock washer in the bearing bolt. Use a piece of masking tape in between the bearing and the rail, and go in small steps (1/8 turn or less) adjusting the nylon set screw -- it's a 1/4-20 screw, so an 1/8 turn is about 0.006" of adjustment. Once you have a smoothly rolling system, remove the tape, go another 1/8 turn on the set screw, and put the lock washer back in. This should get you a tiny bit of preload.
Since you're running hot-rolled rails, you may want to wait on this procedure until you've run it back and forth a bunch to wear the rail to a more uniform thickness. I would actually recommend using your concrete blocks to do this. Each carriage is capable of supporting a minimum of 150 pounds, so this shouldn't cause any problems for the bearings.
Best regards,
Ahren
www.cncrouterparts.com