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The keel and crop are two different things. When they go to roost, their crops should be full and you can feel it.
Being able to palpate the keel bone in a layer is good. A fat layer hen is unhealthy and it will shorten her life and cause health problems. If your flock has free access to a large area to move around in, substrate to scratch through and places to jump/fly up on and are very limited in treats (I prefer to keep it to less than 5 wt% of their total diet), they should be able to eat their complete diet plus whatever they forage without getting overweight.
Use this chart as a guide.