I need to replace the damper felts on a 1942 Steinway B. What would the best felt be for this situation? Do you know what manufacturer currently supplies Steinway? I would like to be able to match the angles of the damper head ends, so pre-cuts are probably not going to work. Is there any functional purpose to the red backing that many of the felts come with? Finally, what is your opinion of treble felts that are either flat or center-stiched? Thank-you for any advice anyone might have.

I routinely use damper felts from Steinway. If you look at their new pianos, the damper felts are not cut at an angle, but as long as you install them with a consistent front edge, they work quite well. Jurgen Goering happens to carry Steinway-style damper felts that are angled at the front in the bass. http://www.pianofortesupply.com/dampers1.html

I doubt that red backed felts are superior to non-backed felts, but that's just my guess. Most older Steinways had non-backed damper felts, IIRC.

Flat vs. center-stitched: I think the center-stitched ones work better, at least in my experience. I've used both styles, but I prefer the stitched ones.