Rewriting git history during git-svn conversion

Hi,

I am converting my team's SVN server to GIT but they aren't ready to transition yet. People are still working out of SVN, so I need to keep the git-svn clone around to do 'git svn fetch' to continue to keep it synchronized with SVN.

Once everyone is ready to switch, and after converting all of the tag-branches to real GIT tags, I plan to push all branches & tags to the new central git repository.

However, before pushing to the central GIT repo, I want to remove some giant directories from the repository history. Specifically some third party library directories. I have found a way to do this here: http://stackoverflow.com/questions/10067848/remove-folder-and-its-contents-from-git-githubs-history

Is it safe to do this while still using git svn fetch? Will it properly continue to convert SVN commits on top of my rewritten history? If not, what changes can I make after I run the commands linked by the URL above so that git svn continues to work normally?

Note that I plan to delete the third party libraries from SVN side and then pull down the changes to git through git-svn, then at that point clean it up (hopefully the git filter-branch command ignores the commit that deleted the files and only hunts down the commits where they were added or modified).

Any guidance on this would be much appreciated.