How "tight" do these get?

They pulled down to around 5mm which was perfect for my application

The tightness of the circle would be small enough; however, I would be certain that the strength of these ties will work for you. I am using mine to hold an electrical cable behind a studded wall in an outside hay barn. It works well there, because there is no practical way to attach the cable inside the cavity between the studs and the outer sheet metal. Also the ties are fastened every 16" so there is very little weight supported by each tie. I would be cautious that the tensile strength of this particular tie will withstand being banged into by a running deer.