There are many small variations to the design of the Allison, Scott Sled, other than those already covered on this web site. Some are made to get around the patent and copyrights. Although the inventors did not specify measurements in their patent applications to prevent any larger or smaller copies of their design, some gave percentages of width to length ratios as in the case of John W. Loy's 'Swallowtail Kite' (application No. 43,108 : patent 4,279,394).
Ray Holland chose to cover his invention with possible alternatives to the main patent application (patent No. 3,767,145).
Some kite manufactures still found ways around the copyrights just by making small alterations to the basic design, round ports, curved leading edges down to the bridle points, just to name a few. Other kite enthusiast chose to experiment with the simplicity of the design and made variations to the vent, seeking to improve on Frank Scott's version of a triangle vent.
Others made double Sleds or Hornbeam kites (right hand side).
Top left, 'Airway Kites of London' vented sled.
Fourth from the left top row, Kenneth and Keith Shields of Ambridge, Pa. with rectangular vent.
Lower four version on the left are versions made by other kite manufactures.