I think of this light re-facing as an institutional re-facing, because the need to preserve as much felt as possible means that the actual hammer nose is barely re-faced: this is only possible where hammer centres are stable and where the hammers have not been re-positioned.
Basic needling of the hammers is done prior to the refacing because, of course, heavy needling distorts the profile.
The first picture shows the Kawai hammers in the process of re-facing, with the proximal sides of the first 4 lower mid section hammers approximately re-shaped:
The second pic shows the Yamaha C3 with the lower mid section hammers done (and how approximately how much felt was removed to achieve this profile):
