Spider slipping on crank?

The smaller cog could put less force as the leverage is less isn't it?. The opposite of using you wheel rim to get best leverage with that Rotafix method.

Probably doesn't make any difference though as I know fuck all about physics :-)

Yes, but somehow I was thinking that with less teeth, there is more pressure exerted on each tooth, reuslting in a greater force to unscrew it, rather than more teeth with the pressure spread between them?

I also have very little knowledge of physics...