  We present the first leading hadron suppression predictions in
$\mathrm{Pb}+\mathrm{Pb}$ and $\mathrm{p}+\mathrm{Pb}$ collisions from a
convolved radiative and collisional energy loss model in which partons
propagate through a realistic background and in which the inelastic energy loss
receives a short pathlength correction. We find that the short pathlength
correction is small for $D$ and $B$ meson $R_{AA}(p_T)$ in both
$\mathrm{Pb}+\mathrm{Pb}$ and $\mathrm{p}+\mathrm{Pb}$ collisions. However the
short pathlength correction leads to a surprisingly large reduction in
suppression for $\pi$ mesons in $\mathrm{p}+\mathrm{Pb}$ and even
$\mathrm{Pb}+\mathrm{Pb}$ collisions. We systematically check the consistency
of the assumptions used in the radiative energy loss derivation - such as
collinearity, softness, and large formation time - with the final numerical
model. While collinearity and softness are self-consistently satisfied in the
final numerics, we find that the large formation time approximation breaks down
at modest to high momenta $p_T \gtrsim 30$ GeV. We find that both the size of
the small pathlength correction to $R_{AA}(p_T)$ and the $p_T$ at which the
large formation time assumption breaks down are acutely sensitive to the chosen
distribution of scattering centers in the plasma.
