I've come upon an efficient way of removing all those pesky tacks in
Ampico bellows.  Piano technicians use a tool called "flush cutters" to
nip flange pins flush to the side.  They are diagonal cutters that have
been ground down so that the cutting edge is flat to the side of the
tool.

Instead of having a knife type cutting surface, it is more like a
chisel.  The sharp point and slope on the inside allows you to get under
the tack head and firmly grab and pry the tack up.  It sure beats tack
pullers, knives or any other trick I've tried.  I did all four bellows
with none broken in about 20 minutes.

Jeff Davis