Is the gravitational field stronger in the transverse plane of a mass than along its axis of propagation? Is the gravitational field stronger in the transverse plane of a mass than along its axis of propagation?   I read somewhere that it was but cannot find the reference again. That is, for a mass traveling at very high velocity, or any velocity I suppose, I read that the gravitational force was stronger in the transverse plane of the mass than it is along its axis of propagation, and wanted to know if this was correct. 
 A: If "transverse plane of mass" means the gravitational attraction perpendicular to the mass's velocity, then you are correct.
There is a weak field approximation to GR call Gravitoelectromagnetism in which there is an $\vec{E_G}$ and $\vec{B_G}$ which obey equations similar to Maxwell's equations for $\vec{E}$ and $\vec{B}$ of electromagnetism.   $\vec{E_G}$ is the acceleration caused by a mass (eg: for a mass M at rest $\vec{E_G}=\frac{-GM\hat{e_r}}{r^2}$), and  $\vec{B_G}$ is the angular velocity $\vec{\omega}$ that a spinning mass with angular momentum causes to other objects.
$\vec{E_G}$ and $\vec{B_G}$ transform just like $\vec{E}$ and $\vec{B}$ when viewed from a velocity boosted frame. Therefore, if we boost an at rest mass that is not spinning (ie: $\vec{B_G}=0$), we get
$$
\begin{align}
\
     E'_{G \ parallel} &=E_{G \ parallel} \\
E'_{G \ perpendicular} &=\gamma E_{G \ perpendicular}
\end{align}
$$
The field lines of $\vec{E'_G}$ (ie: acceleration) are bunched out perpendicular to the boost direction.  I think this is the effect you read about.
