As I was typing last night it occurred to me the name of SE Felt. I kind of believe that most of the time, things work best when you use what was designed for them. The felts that worked best were also the most expensive, costing anywhere from about $0.10 to about $0.50 (plus freight) which may not seem that expensive but you (we) did use a lot of them as you often changed them when the spool was changed. Of course this depended upon the size of the takeup spool.
the factory felts were fiber specific meaning that it was a mix of fibers including a percentage merino wool. The fibers in the felt were also oriented so that they looked like the top end of a box of soda straws. They were also specific densitities or weights such as a 24 designation might mean 24 grams/cubic cm and a 32 was that many grams per cubic cm.
We were able to find a supplier that could make the sizes and they were about 1/3rd as expensive up front, however the densities were not consistent, the fibers were randomly orientated and you often replaced them more frequently than the factory felts. They did work if you stayed on top of the process.
I have no idea of what current felts are like and did not even know that SE was still in business.
They were good to work with and did everything that they could to provide what we wanted or needed. I hope they still offer that level of customer service.