S-patches have many nice mathematical properties. It is known since their
first appearance, that any regular S-patch can be exactly converted into a
trimmed rational B\'ezier surface. This is a big advantage compared to other
multi-sided surface representations that have to be approximated for exporting
them into CAD/CAM systems. The actual conversion process, however, remained at
a theoretical level, with bits and pieces scattered in multiple publications.
In this paper we review the entirety of the algorithm, and investigate it from
a practical aspect