261 has roller bearings on all axles.
With regards to the cylinder casting there is only one real fix. Replace the cylinders. There were design or material problems with the original castings and the NP replaced a number of the Q3 cylinders with newer castings. Take a look at the 2153 out back.
Also look at the Austin Steam Train Association website. They are in the process of replacing the cylinders on the 786.
2156 is a neat engine but it has more problems than the cylinders.
Anything happening with 328?
If you have more questions backchannel me.
Paul Dalleska