I notice that a lot of people use the AL angle and roller bearings for their axis's. I notice that VXB has some linear bushings, 4 for $25, but not many, if any, people use them. Is there something wrong with them? Is it because they're not adjustable? Are they poor quality? It would seem that they would work really well. Is it because they don't really work on steel pipe from HD or Lowe's? Any insight would be greatly appreciated.