DV Info Net - Best bearings for a balance rig?

I've been researching parts for building a DIY balance rig, and some of the key components are bearings. Aside from low cost, what should one choose?

For lowest stiction, I would think that an open bearing with graphite lubricant would be the best choice. However, if it's not sealed, dust, lint, and sand (at the beach or desert) could gum up the works. Many of the small sealed bearings use grease, rather than oil, and that could add resistance. One could potentially use felt as a seal on an open bearing to attempt to keep things clean.

So, the questions are...

1) Open or closed?
2) Is grease OK, if sealed?
3) If closed, metal or plastic seal?
4) ball or roller? (I figure that ball is adequate.)

For bearings with an axial load, for instance, the main rotational bearing, and the "door hinges" in the arm, I'm thinking that 40 degree ball bearings would be best.

It's really too bad that flex joint bearings don't rotate further. They seem to have the lowest stiction, and have no maintenance issues, if you don't overstress them. But they only deflect by +/- 15 degrees or so, and they have some spring forces. Flex bearings wouldn't work on the sled, but it would be cool if they could be used in the arm. As an example, think of the mouth of a Tic Tac container.

I'm probably over complicating things, but it's always good to learn from those with experience before spending the cash.