  This work confirms the stability of a class of domain wall lattice models
that can produce accelerated cosmological expansion, with pressure to density
ratio $w=-1/3$ at early times, and with $w=-2/3$ at late times when the lattice
scale becomes large compared to the wall thickness. For walls of tension
$T_{I}$, the relevant X type junctions could be unstable (for a sufficiently
acute intersection angle $\alpha$) against separation into a pair of Y type
junctions joined by a compound wall, only if the tension $T_{II}$ of the latter
were less than $2T_{I}$ (and for an approximately right-angled intersection if
it were less that $\sqrt{2} T_{I}$) which can not occur in the class considered
here. In an extensive category of multicomponent scalar field models of forced
harmonic (linear or non-linear) type it is shown how the relevant tension --
which is the same as the surface energy density $U$ of the wall -- can be
calculated as the minimum (geodesic) distance between the relevant vacuum
states as measured on the space of field values $\Phi^i$ using a positive
definite (Riemannian) energy metric $dU^2=\tilde G_{ij} d\Phi^i d\Phi^j$ that
is obtained from the usual kinetic metric (which is flat for a model with
ordinary linear kinetic part) by application of a conformal factor proportional
to the relevant potential function $V$. For suitably periodic potential
functions there will be corresponding periodic configurations -- with parallel
walls characterised by incrementation of a winding number -- in which the
condition for stability of large scale bunching modes is shown to be satisfied
automatically. It is suggested that such a configuration -- with a lattice
lengthscale comparable to intergalactic separation distances -- might have been
produced by a late stage of cosmological inflation.
