1.) Uninstall any Dropbox on your device.
2.) Download and install this : http://www.mediafire.com/?yjvzu2mdrybdrqt
3.) Login, and after about 10 mins you'll get an email that says you've got 23GB of space more
4.) Uninstall modded app, and install original if you want.
No need for root. Don't know if it works on froyo, but it works great for me on MS2 and CM9
I'm not responsible for any damage to your account.
Proof that it works :
Mirror : http://www.box.com/s/b87a44a72027dde0afb9
Doesn't work anymore.
Wait for a new build.prop guide.