I do halves and doubles sometimes. It's hard to keep the proportions straight even at 1:2 or 2:1. I think this is due to various quirks of nervous system, eithe

I do halves and doubles sometimes. It's hard to keep the proportions straight even at 1:2 or 2:1. I think this is due to various quirks of nervous system, either mine or humans in general. That said, I'm not sure a kitchen slide rule would help. PS I own two, a Pickett and a Dietzgen.