No large seed is safe from the voles/fieldmice so:
For climbing french beans, 4 seeds in a 4" pot. Expect to get 3 at least up . 1 pot per stick
For runners (saved seed), 40 beans in 3" compost in mushroom tray with single sheet of newspaper to line. Planted out @ 2 per stick plus a bean or two as spare/later crop. Problems as described-rooks pull them out, few slugs now with no-dig.