Result

. FWIW I now have 8 inch blades, the only sprung ones I could find in black and the absolute longest the screen will accomodate. They got quite a lot of use during holiday trip to/from I.O.W recently without fuse blowing. I have topped up the grease in motor in the past, although it wasn't desparately low, so there is some leeway in motor current draw if well lubed.