If you are looking to reduce friction/wear in the phenolic blocks where the torque tubes pass through, you can oversize the holes and then fit Rulon shoulder bushings (available from McMaster Car). I think that Jim P and Bob Farnum came up with this idea and I have used these liberally in my plane (elevator, ailerons, and rudder), all with good results. The structural portion of the mounts should still be phenolic, but if you drill these out to accommodate the bushing, it is best to make outside dimensions of the phenolic larger, or reinforce with glass, so as to not lose any structural strength or rigidity.

Cheers,
Jay