I think that if a fox does come hunting you are going to lose some either way. We built a run for our first chooks many years ago and they just flew straight out. We clipped a wing each and they still just flew straight out. Now we never clip wings or have them in a pen. They free range over about 5 acres near the buildings and occasionally a fox does come - sometimes we have lost lots, sometimes it's a hen with newly hatched chicks in the undergrowth which we haven't managed to catch to put in a coop.
Things to do to reduce the likelihood of foxes getting them, apart from a totally fox-proof enclosure, is making sure they don't come out too early in the morning and that they are closed in before dusk. We also try to make sure we are about approaching dusk, making a lot of noise, dogs barking etc just to let the foxes know we are there.
Our hens are very independant creatures and would hate to be curbed by being shut in, but there is plenty of cover for foxes so I know I will lose more
Oh and the other day Yellow Leg who was the most wonderful and independant maiden Scots Grey hen (in that she kept herself well away from any cockerels for years) was flattened on the road by a callous, careless, speeding driver. So if the foxes don't get them, the boy racers will.