Seeing as Spini's spinner had got so unbalanced that it was almost useless, I decided it was time for an upgrade:
It's a single tooth blade based on Why Wait?'s, made from 2mm mild steel. Managed to get it so nicely balanced that it only starts to vibrate around a little when on full throttle.
I need to tweak the motor mount a little as the blade currently sits about 2mm off the ground, meaning it can't bite scoops well yet. The bite seems to be pretty small most of the time sadly, though when it does get a good bite it's pretty impressive; threw Sir Lift-a-lot about a foot in the air in one test. I think the lack of bite's just due to the high speed and small diameter of the blade; hopefully it'll improve as work continues..