  We address in this work the general features of a possible compact stars
composed by elementary fermions beyond the quark level. The {\it locus} of
these hypothetic objects in the mass-radius plane is constructed for the
maximum mass (minimum radius) of the sequence of models in terms of a
compositeness scale only, and in fact this approach applies for any composite
model postulating fermions at or beyond the preon level. We point out a
constraint on the preon mass arising from the applicability of the General
Relativity structure equations, leading to the questioning of the hypothesis of
light preons if the preon scale is high, provided classical compact objects are
enforced. Some remarks on the existence of superdense stars of astrophysical
and primordial origin are made and discussed.
