The company took the basic Challenger design and incorporated many changes, including mounting the engine upright allowing larger propellers and the Rotax gearbox to be mounted, lengthening the tailboom and enlarging the tail vertical surface to increase stability, shortening the ailerons and replacing control cables with torque tubes.

The optional Dacron covering on the Challenger was replaced with Superflite standard aircraft fabric, the fuselage was lengthened to give more backseat room and the nosecone was reduced in size to provide better over-the-nose visibility.

The design was also streamlined to reduce drag and round cross-section wing struts were replaced with aerodynamic extrusions.

[1] Regarding the landing gear improvements reviewer Andre Cliche, author of the Ultralight Aircraft Shopper's Guide, said: the Excalibur features a bungee suspension on mainwheels.

That's an improvement over the Challenger whose rigid main gear tubes kinked too many times during rough landings.