  The requirement of a large pseudo-rapidity gap to select diffractive DIS
events at HERA restricts the kinematically accessible region of phase space for
a significant range of $Q^2$, $\beta$ and $\xpom$. Consequences of this include
a breakdown of $\xpom$-factorization in large rapidity gap diffractive samples
and an enhancement in the relative contribution of quark-antiquark-gluon
processes over dijet processes in the diffractive DIS sample.
