[1] Slingsby had introduced double curvature fuselage panels made of glass reinforced plastic (GRP) into their previous design, the T.49 Capstan and they remodelled the front of the wooden fuselage of the Skylark 3 in this material for the Skylark 4, introducing a reclining pilot's position and smoother canopy line.

Though the previous wing planform, span and area was retained, its ailerons were extended to increase the rate of roll and the outer panels used a different airfoil section, the more cambered NACA 6415, to give a better lift distribution.

The Gaboon ply was applied diagonally across the ribs, which produced a very smooth wing-surface that is claimed to generate a laminar airflow.

The cockpit is immediately ahead of the wing leading-edge, enclosed with a lengthened perspex canopy, and the Skylark 4 was 80 mm (4 in) longer than its predecessor.

In 1963, at Junin, Argentina the four Skylark 4s of the British team were placed consecutively 8-11th,[4] and a single entry came 9th in 1965 at South Cerney, UK.

[6] Data from Ellison 1971, p. 218The World's Sailplanes:Die Segelflugzeuge der Welt:Les Planeurs du Monde Volume II[7]General characteristics Performance

The World's Sailplanes:Die Segelflugzeuge der Welt:Les Planeurs du Monde Volume II (in English, French, and German) (1st ed.).