It seems that not using a Maxwellian distribution of velocities in your dust swarm, will lead to some obstacles in grain formation that go away when you do. "Lucky" low velocity particles can suffer a sufficient number of low velocity sticking collisions to increase in size by a factor of ~ 50 such that they can become the seeds of planetesimals. Marks left by the nebula wind.
SEE Windmark et al. :http://arxiv.org/abs/1208.0304