A phenomenological model linking the macroscopic volume from dilatometry with the microscopic free volume from positron annihilation lifetime spectroscopy is presented, The temperature dependences of both quantities enable to obtain the so-called initial temperature T-i at which dynamic free volume change sets in, the corresponding initial volume V-i, and subsequently, all free volume characteristics. Application of this model on the literature data of a typical low-molecular weight glass former, o-terphenyl, leads to the findings that (i) T-i congruent to T-K the Kauzmann temperature and (ii) a packing fraction of the extrapolated equilibrium liquid at T-i is close to the closest regular packing of hard spheres. The published viscosity-temperature data over 12 decades of magnitude are correlated with the free volume hole fraction f(h), as determined from the PALS results, via the WLF-Doolittle type equation. These findings indicate that the orthopositronium (o-Ps) is able to detect the part of the total free volume distribution which is relevant for the viscosity over the measured temperature interval from T-g up to similar to 1.5T(g). In addition, the change of the free volume hole behavior above T-r = 1.25T(g), lying in the vicinity of the crossover temperature T-c from the idealized version of mode-coupling theory, is critically analyzed within a modified bubble concept (the equilibrium interaction of o-Ps with the soft matrix).