I don't have any parameters that I can give, but when we did our data import at another company, we had to change a bunch of settings to improve the performance for batch import. These settings made the system almost unusable for interactive work. It was 8 years ago on PDMLink7, so maybe PTC has documented what needs to be set or improved the processes so batch and interactive can coexist.
I have seen similar poor performance with Import in 10.0; Open in Solidworks and Save to Workspace was a multiple faster.
Do remember though that Import is using SolidWorks and Memory so you can really only Import One Top Level assembly at a time, with drawings seems to make a bit worse.
Be Sure to
1. Large Assembly Mode Off
2. Updated SW Models to SW 2012/ Rebuilt Assemblies w/o Large Assembly Mode and found all suppressed components, etc...
If Data already in a database, their are 3rd Parties that will bulk migrated the data; Was involved in a project in 9.1 that bulk migrated last revision of multiple solidwork databases.. (last revision)