I don't see any responses yet so I'll give a few hints - hope this isn't too late.

use the remastering process as documented (I don't have the link here) which is more or less:
unpack ISO, unpack compressed FS, copy compressed FS, chroot and change as desired, create compressed FS, create new ISO

while working in the chroot environment, use apt-get to remove large packages like openoffice.
remember to use "apt-get --purge remove <package>"

If you do not need it, get rid of KDE, or at least some of the languages, and either replace it with something lighter like fluxbox.

If you need specific help with parts of the remastering process, post questions. there are a lot of detail left out of the above brief summary, like mounting and unmounting /proc, copying a resolv.conf, and cleanup, etc.