Our bending tools are fixed radius and are not adjustable for different hoop sizes. Example our 20 ft. benders will produce a complete 20 ft. circle when six 10'6" lengths are bent and joined together and compressed. with that in mind bending only three lengths produces a 20 ft. wide hoop about 9 1/2 feet tall when compressed and installed into ground stakes. 

With that said, you can make a usable 16 ft hoop using a 20 bender by simply bending less tubing 2 and 1/2 sections instead of 3 sections into the same radius. The bottom ends of the hoops will be pointing outward a little, then will not be going straight into the anchor pipes. Therefore the anchor pipes must be set in the ground at an angle to match the hoops.