  In 2002, Isenberg-Mazzeo-Pollack (IMP) constructed a series of vacuum initial
data sets via a gluing construction. In this paper, we investigate some local
geometry of these initial data sets as well as implications regarding their
spacetime developments. In particular, we state conditions for the existence of
outer trapped surfaces near the center of the IMP gluing neck and thence use a
generalization of the Penrose incompleteness theorem to deduce null
incompleteness of the resulting spacetimes.
