  In color dipole gBFKL dynamics, we describe the emerging gBFKL phenomenology
of a subasymptotic energy dependence of the diffraction slope and discuss
possibilities of testing the gBFKL predictions in exclusive photo- and
electroproduction of vector mesons $V$ at HERA. A substantial shrinkage of the
diffraction cone $\gamma^{*}p\rightarrow Vp$ processes from the CERN/FNAL to
HERA range of energy $W$ is predicted. This subasymptotic shrinkage is faster
than expected from the small slope of pomeron's Regge trajectory
$\alpha_{\Pom}'$. We point out that the diffraction slope is a scaling function
of $(m_{V}^{2}+Q^{2})$, what relates production of different vector mesons.
