  Soft-QCD effects of quark-level form factors in $\gamma\gamma$ decay of
$B_s$-mesons via $D{\bar D}$ intermediate states, suggested by Ellis et al, are
examined in the "Salpeter" model [reinterpreted in terms of the Markov-Yukawa
Transversality Principle (MYTP)] when formulated on a covariant light front
(null-plane). The gluonic kernel in the infrared regime which generates the
constituent mass via standard $DB{\chi}S$, is calibrated to both $q{\bar q}$
and qqq spectra, meson mass splittings, pion form factor,and other parameters.
With this check, an exact evaluation of the $D{\bar D}\gamma$ vertex form
factor $F(\alpha)$ (normalized to F(0)=1), gives a multiplicative effect of
$F^2(\alpha)$ on the $B_s \Rightarrow \gamma\gamma$ amplitude via D-meson
triangle loop, where $\alpha$ = $(p^2+M^2)/M^2$ is the off-shellness parameter
of the exchanged D-meson of mass M and 4-momentum $p_\mu$, and is a variables
of the (internal)loop integration. Unfortunately, the $F^2(\alpha)$ effect
decreases the loop amplitude by a factor of 30 w.r.t. the point hadron value,
resulting in a reduction of 3 orders of magnitude in long distance (hadronic)
contributions to the $B_s \Rightarrow \gamma\gamma$ decay rate, thus greatly
impairing the visibility of such modes. PACS: 11.10.St ; 12.38.Lg ; 13.20.Gd ;
13.40.Hq Keywords: $B_s$ radiative decay; Soft-QCD; Vertex-Fn; Form-factor;
Markov-Yukawa-Transversality Principle; Salpeter eq; Cov. light front
