Put your posts on the outside of the box and top them with tennis balls with suitable holes in them to go over the posts they spread the load very well .
Slugs & snails just love having a slug or snail fest on the young sweeet tender plants .
Pigeons , sparrows and all sorts of other birds can easily kill you leafy sweet greenery .
Some of my spring greens look like trawler nets .
The fine 4 mm white nylon mesh netting is good to keep out butterflies so is cheap white frost fleece . Round here farmers grow a lot of greens under fleeces for precisely that reason as well as to keep the ridged rows free of cold and frost . .That'll keep the birds out but not the cabbage whites.
It's a bit of a conundrum because the only way to stop the butterfly's is a really fine mesh, which also stops the pollinators.
Brassica's don't need pollinating as far as I'm aware, so in an ideal world you'd have 2 separate netted areas, one with a fine mesh for the cabbages and one with a course mesh for things that need pollinating.
I've never found it necessary to net beans full stop mind. The birds don't seem to bother about them and I've never had a rabbit problem.
So I'm probably not much help.
" Beer in a saucer and a flash light , skewer & salt at night " . As roger Rabbit said " it get's em every time , much better than a , shampoo and hair cut Doc " 
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Something yeasty & farty ?
should have dosed round the whole garden with slug and snail killer pellets we do it twice a year and kill hundreds before they get in the potsWell...the runner and dwarf beans SWMBO planted in pots have been fairly decimated by the b'stards! Found two snails under the rim of one pot then a big fat slug on the ground when I moved the pots.
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Doesn't bode well for when the 50 go in the ground
