From my own experience another nice side effect of the fake felt is no dust.

Since the fibers themselves are some sort of plastic, they don't fray and break off. And because they are affixed in a strip compressed directly between the condenser and carrier, they are completely covered when the condenser is in the lowered position, which is how I keep it when not in use to keep airborne dust out of the bellows. Thus they gather no dust themselves.

And finally, because they are in a compressed state during all of the downtime, the adhesive stays firmly attached to the bottom ridge of the condenser housing. Yet because they're plastic, when you do lift the head they spring right back up. And I'm also pretty anal regarding dust in my darkroom, as I routinely use double-glass AN negative carriers for optimum sharpness.

I did try the adhesive weather stripping. But even using the thinnest I could find it still wedged the cold light diffuser up too far up from the negative. Then I tried attaching the stripping all the way around the outside of the condenser, with only a thin portion protruding below the bottom to act as a seal. But the adhesive, being subject to a constant lateral (vertical) force relative to the sticky surface plane, constantly popped off. And the new, larger circumference was too large for my standard carriers, which the condenser housing just barely covers.

Ken