Talk Morgan Forums Morgan Sports Cars Morgan Plus Four, Supersport & Plus Six (CX & CXV Generation Vehicles) Plus Six wiper judder - advice requested

Just out of general interest. I used a rifle trigger pull gauge to measure the Plus Six wiper arms spring force at the wiper blade.
The measurement right at the end of the wiper arm at the wiper blade was consistent on all three arms at 1.5 lb ( 0.6803 Kg ). This figure was recorded just as the wiper blade started to lift from the windscreen.