For what it is worth- I have shaped and polished several bars on large pianos by restringing one half of each treble section at a time. It is a dirty job and somewhat awkward filing the bar while watching a mirror placed on the keybed- but very doable. Not a bad idea to check and pull the bridge pins if necessary while you are that far anyway. Everything else said about the spacing and stringing was good too. Once I even carefully routed out the duplex bar in front of the cappo to seat a brass rod of correctly higher dimension to give a better angle of termination- somewhere between 17 and 20 degrees. No more than 21, for that range. good luck- dennis johnson St. Olaf (never been so burned out by fall break, and looking forward to the calm).
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