  Some close-in gaseous exoplanets are nearly in Roche-lobe contact, and
previous studies show tidal decay can drive hot Jupiters into contact during
the main sequence of their host stars. Improving upon a previous model, we
present a revised model for mass transfer in a semi-detached binary system that
incorporates an extended atmosphere around the donor and allows for an
arbitrary mass ratio. We apply this new formalism to hypothetical, confirmed,
and candidate planetary systems to estimate mass loss rates and compare with
models of evaporative mass loss. Overflow may be significant for hot Neptunes
out to periods of $\sim$ 2 days, while for hot Jupiters, it may only be
important inward of 0.5 days. We find that CoRoT-24 b may be losing mass at a
rate of more than an Earth mass in a Gyr. The hot Jupiter WASP-12 b may lose an
Earth mass in a Myr, while the putative planet orbiting a T-Tauri star
PTFO8-8695 might shed its atmosphere in a few Myrs. We point out that the
orbital expansion that can accompany mass transfer may be less effective than
previously considered because the gas accreted by the host star removes some of
the system's angular momentum from the orbit, but simple scaling arguments
suggest that the Roche-lobe overflow might remain stable. Consequently, the
recently discovered small planets in ultra-short-periods ($<$ 1 day) may not be
the remnants of hot Jupiters/Neptunes. The new model presented here has been
incorporated into Modules for Experiments in Stellar Astrophysics (MESA).
