  In this brief note we would like to discuss, in a simple model system, the
conditions under which the discrete light cone quantization framework should be
trusted as an approximation scheme, with regard, in particular, to the size and
mass of the system. Specifically, we are going to discuss ``quark-antiquark''
bound states in 1+1 dim., for which a natural size is provided by analogy with
a ``two points and a spring'' system, and show that the condition for obtaining
a reliable estimate is the same as the one derived in a recent paper for black
holes in matrix theory.
