  In this paper, we consider the chain of resonances in the Kepler-80 system
and evaluate the impact that the additional member of the resonant chain
discovered by Shallue & Vanderburg (2018) has on the dynamics of the system and
the physical parameters that can be recovered by a fit to the transit timing
variations (TTVs). Ultimately, we calculate the mass of Kepler-80 g to be $0.8
\pm 0.3 M_\oplus$ when assuming all planets have zero eccentricity, and $1.0
\pm 0.3 \ M_{\oplus}$ when relaxing that assumption. We show that the outer
five planets are in successive three-body mean-motion resonances (MMRs). We
assess the current state of two-body MMRs in the system and find that the
planets do not appear to be in two-body MMRs. We find that while the existence
of the additional member of the resonant chain does not significantly alter the
character of the Kepler-80 three-body MMRs, it can alter the physical
parameters derived from the TTVs, suggesting caution should be applied when
drawing conclusions from TTVs for potentially incomplete systems. We also
compare our results to those of MacDonald et al. (2021), who perform a similar
analysis on the same system with a different method. Although the results of
this work and MacDonald et al. (2021) show that different fit methodologies and
underlying assumptions can result in different measured orbital parameters, the
most secure conclusion is that which holds true across all lines of analysis:
Kepler-80 contains a chain of planets in three-body MMRs but not in two-body
MMRs.
