The .spx exporter in Revit has the ability to limit the number of Userfields exported from Revit. I think it would be a great idea to have the same function built into the Navisworks Exporter. Currently, it exports all Userfields and values and this blows up file sizes quite a bit. Most 4D Pro users do not use 90% of the Userfields that come with objects, this would allow us to just export the ones we use.