  We present a way to create small yet difficult model counting instances. Our
generator is highly parameterizable: the number of variables of the instances
it produces, as well as their number of clauses and the number of literals in
each clause, can all be set to any value. Our instances have been tested on
state of the art model counters, against other difficult model counting
instances, in the Model Counting Competition. The smallest unsolved instances
of the competition, both in terms of number of variables and number of clauses,
were ours. We also observe a peak of difficulty when fixing the number of
variables and varying the number of clauses, in both random instances and
instances built by our generator. Using these results, we predict the parameter
values for which the hardest to count instances will occur.
