Use 3/8" metal rod for the pegs. Even 7/16 is not overkill. Run your pegs about 2" apart. Use your washers or whatever alignment you use on all your forms. Use zip ties. Be sure your hose is completely deflated before tie down. Keep the hose dead center. Tie down as tight as you can muster. There is this u tube created belief that you must use mule tape for tie down but I've used the same paracord many times.
If you are in the production business, a conventional form will better suit you. If you are an experimenter the top less gives you immediate flexibility.