In winds under eight knots true, boats make the best progress sailing with apparent wind around 90-degrees and then jibing. A sail for these conditions is made from a .5 to .6 oz. high performance nylon like Airx or Superkote, has a flat entry for sailing closer to the wind, and has a reduced area to make it easier to fill in light winds.
The heart of faster spinnakers is the construction method. The panel layout UK Sailmakers uses is called Matrix, which is a full radial layout that features narrow panels, each oriented to better align the threads in the cloth with the primary loadpaths in the spinnaker. This is the most effective way to reduce distortion and make the strongest sail for its weight.
Each panel is shaped on all four sides in order to create a smooth round sail. For one sail be so versatile, it needs to hold its shape without distorting. Distortion becomes most obvious when close reaching. Spinnakers made with generic nylon cloth stretch in the middle, causing their leeches to harden or hook; which reduces driving power, creates drag, and increases heeling. The only way to prevent distortion, without using too heavy a fabric, is to use performance nylon spinnaker cloth like those made under the Superkote and Airx names. These materials have the same strength and stretch resistance of one weight heavier standard nylon.