The Tumble Weed is obviously inspired by the Astron Sprite, but it is not an exact downscale. The nose cone and body tube of the TW are both shorter in relation to the overall size of the rocket than the same components are in the Sprite. The motor also has a much tighter fit in the body tube of the Tumble Weed than was the case with the motors in the Sprite. I did a fair amount of sanding of the inside of my TW's body tube in order to loosen the fit somewhat, based on the hypothesis that a tight fit translates into a greater build-up of pressure when the ejection charge fires. My thinking was that this would cause the motor to be pushed backwards with so much force that the motor hook could not retain it. If the motor was allowed to move more easily, the ejection gas pressure would be vented more quickly and consequently the force acting on the motor would not be as great. The ejection charge in 13mm motors produces much more force than is necessary to move them rearward to the recovery position in the Tumble Weed.The Fliskits Tumbleweed is a downscale for 13mm motors.