So, Tim, long time no see. If you really like short fat rockets go to
Sam's Club and check out the doggie igloos They are perfect parabolas,
come in two halfs for that payload ejecting clamshell effect and have a
door for the dog to go in and out of. Also looks like they fit a
standard trashcan, or will with slight mods. I'll leave the fins and
motor(s) choice to you.