  The stabilisation of the dilaton and volume in tree-level flux
compactifications leads to model independent and thus very powerful existence
and stability criteria for dS solutions. In this paper we show that the sizes
of cycles wrapped by orientifold planes are scalars whose scalings in the
potential are not entirely model independent, but enough to entail strong
stability constraints. For all known dS solutions arising from massive IIA
supergravity flux compactifications on SU(3)-structure manifolds the tachyons
are exactly within the subspace spanned by the dilaton, the total volume and
the volumes of the orientifold cycles. We illustrate this in detail for the
well-studied case of the O6 plane compactification on SU(2)xSU(2)/Z_2xZ_2. For
that example we uncover another novel structure in the tachyon spectrum: the dS
solutions have a singular, but supersymmetric, Minkowski limit, in which the
tachyon exactly aligns with the sgoldstino.
