For large static files you should make your own local extension and then either load it "onboot" or when needed.
If you insist on storing large files in your backup, which will slow down shutdown and booting, you should either use the gui cpanel/Backup/Restore to add the files or manually add them to /opt/.filetool.lst and remove the leading slash, for example:
usr/local/share/fonts/xxx.ttf
and not
/usr/local/share/fonts/xxx.ttf