Thanks! I just noticed that the URL for the i386/i686 iso was wrong:
+ <url>http://cdimage.debian.org/cdimage/stretch_di_rc2/i386/iso-dvd/debian-stretch-DI-rc2-amd64-DVD-1.iso</url>
Should be http://cdimage.debian.org/cdimage/stretch_di_rc2/i386/iso-dvd/debian-stretch-DI-rc2-i386-DVD-1.iso :)
