One of the main aspects when testing floating offshore platforms is the scaled mooring system, particularly with the increased depths where such platforms are intended. When the existing testing facilities do not have enough available space, the use of truncated mooring systems with a similar behaviour to the real mooring system could be an interesting option. As part of the development of SPAR platform made of concrete for FOWTs a station keeping system with catenary shaped lines was selected. The test facility available for the planned experiments presented an important width constraint. Then, an algorithm to optimize the design of the scaled truncated mooring system by using different weights of lines was developed. The optimization process adjusts the quasi-static behaviour of the scaled mooring system as much as possible to the real mooring system within its expected maximum displacement range, where the catenary line provides the restoring forces by its suspended line length.