  We have simulated a common envelope interaction of a 0.88-M$_{\odot}$,
90-R$_{\odot}$, red giant branch star and a 0.6-M$_{\odot}$, compact companion
with the smoothed particle hydrodynamics code, Phantom, from the beginning of
the Roche lobe overflow phase to the beginning of the self-regulated inspiral,
using three different resolutions. The duration of the Roche lobe overflow
phase is resolution dependent and would lengthen with increased resolution
beyond the $\sim$20 years observed, while the inspiral phase and the
post-common envelope separation are largely independent of resolution. Mass
transfer rates through the Lagrangian points drive the orbital evolution during
the Roche lobe overflow phase, as predicted analytically. The absolute mass
transfer rate is resolution dependent, but always within an order of magnitude
of the analytical value. Similarly, the gravitational drag in the simulations
is close to the analytical approximation. This gives us confidence that
simulations approximate reality. The $L_2$ and $L_3$ outflow observed during
Roche lobe overflow remains bound, forming a circumbinary disk that is largely
disrupted by the common envelope ejection. However, a longer phase of Roche
lobe overflow and weaker common envelope ejection typical of a more stable
binary may result in a surviving circumbinary disk. Finally, we examine the
density distribution resulting from the interaction for simulations that
include or omit the phase of Roche lobe overflow. We conclude that the degree
of stability of the Roche lobe phase may modulate the shape of the subsequent
planetary nebula, explaining the wide range of post-common envelope planetary
nebula shapes observed.
