Filter points from LiDAR upon import to terrain model

I have LiDAR of an irregular stone object that I'm attempting to bring into PowerGEOPAK as a terrain, using the "Create from Point Cloud" tool.  It's working well, but my data needs cleaning up.  In the process of importing, it is filtering out 90% of the original data, which seems fine.  But I have many tiny spikes in the resulting surface.  There are too many to clean up by hand (I've tried).  Are there any parameters I can use during the import process that might smooth the surface, or at least remove isolated spikes?  I'm also working with Leica to see if there is any way to clean it up in Cyclone before attempting this with GEOPAK.  

Any advice would be helpful!  

Thanks,

Frank Boston, Michigan DOT