Some moderns have a spring wrapped around the drum , brake lathe have a band to wrap around the drum while cutting that maybe leather ?! I’ve thought about using a screen door spring and wrap around the drum ?! I tried using RTV on the shoes but that experiment failed . When I backup braking no noise and if I hold the pedal down backing going forward I get a couple of noiseless stops . I paid good money for the woven fiber with the copper wire , brand new along with new iron drums . Tapering the shoe ends was only a temporary fix , taking the drums off , dropping them on the ground and cleaning the backing plates, shoes , springs , etc is also a temporary fix . One last tought wonder if groves cut across the shoe faces would help, 2 or3 perpendicular on the shoe ?