You’re welcome for the advice. You did express concern about chicken hawks. A valid concern. Trees will not be a sure fire protection, as others noted. Personally, I would not house 70 chickens in 700 square feet, and it is the MINIMUM, not the best, unless you have blinds, roosts, levels...
I agree, once and done is best!
70 chickens, 10Sq ft each = 700 sq ft minimum space.
A half acre is 21,000 + sq ft.
So, you can reduce pen size to help manage coverage, as one option. You could have a few smaller pens. You could create a mobile coop that gets moved to fresh grass...