Even if you know how to edit, you may not be able to do it correctly for foam. For example, you cannot make small pieces out of foam. You need to join the small pieces into one big pieces logically without altering the final model. Stealth may have a tutorial on how to make the edits in YouTube. Search for "the Hero Tutorials."
I edited some of the files for foam a few weeks ago. Hopefully this is a start.
