We generalise a recently proposed concurrent flexibility metric to overcome some of its shortcomings. We show that these shortcomings can be removed if one selects an optimal subset of variables for which the concurrent flexibility is determined. The flexibility of the remaining variables does not play a role in the determination of the flexibility of the system. We present a preliminary experimental evaluation of the improvement in concurrent flexibility that can be obtained by comparing some (approximation) algorithms. Their performance on several benchmark sets is evaluated. As a result, in some cases the concurrent flexibility of an STN can be enhanced by 20-50%.