• Uninstall any other instances of dropbox (either official or unofficial)
• Install my APK
• Login & wait for the confirmation mail!
• If you haven't received the confirmation mail after 30 minutes, try uninstalling the app, the installing it again and login. BUT, it doesn't work for everyone. Haven't figured out why yet.
• After getting the extra space, you can go back to official dropbox builds (uninstall mine first).
Thanks to theos0o from XDA