We show that the maximum shower depth distributions of Ultra-High Energy
Cosmic Rays (UHECRs), as measured by fluorescence telescopes, can be augmented
by building a mapping to observables collected by surface detectors. The
resulting statistical improvement of such augmented dataset depends in a
universal way on the strength of the correlation exhibited by the mapping.
Building upon the publicly available data on "golden hybrid" events from the
Pierre Auger Observatory we project possible improvements in the inferred
composition of UHECRs for a range of possible mappings with varying correlation
strengths.Comment: 8 pages, 6 figures, method correcte