Ok, I tested full backup to FTP on both servers and it worked on both with backup files of over 400mb. I suspect the error message you got was from incorrect FTP server credentials. Either that or it was just an intermittent error that I cannot reproduce. You can import them back in, but you have to extract them on your home pc, and import them piece by piece. What cPanel is warning you is you can't just upload the full backup, and have it all automatically import.