  We propose to perform a combined analysis of $B \to \pi\pi$ and $B_s \to K^+
K^-$ modes, in the framework of a global CKM fit. The method optimizes the
constraining power of these decays and allows to derive constraints on NP
contributions to penguin amplitudes or on the $B_s$ mixing phase. We illustrate
these capabilities with a simplified analysis using the recent measurements by
the LHCb Collaboration, neglecting correlations with other SM observables.
