What about adding *.rar archived files to the uploadable file types?
Here are some points why to:

You can Make parts out of an archive which's over the j2o upload limit (2MB)

You can use about 30 settings to edit how to compress your archive (like picture compression, text compression, make parts, format target disk, make a progressive archive (solid), add auto run command after extracting...)

And The Most important thing for j2o:

Higher Compression Quality (up to 35% more compression as Win Zip!!!! )

Download Win Rar Here

Now: What do you think about that?