carbon copy cloner - delete files with scheduled task

I recently downloaded carbon copy cloner (ccc) and have been trying it out. Everything is going great, it has created backups of two of my 1tb hard drives with no problem. Unfortunately one of the hard drives is basically full (2 or 3 gb left at the moment) and I noticed that ccc will not allow me to schedule a backup with the 'Delete Items that don't exist on the source' option.

I suppose this is because when I did the initial backup with this selected it took a very long time to do the backup, and if I wasn't running out of space on the drive it would not be a problem. Unfortunately the main drive has 1.96 gb available, but the backup only has 99.4 mb available, and I am worried what will happen when the next scheduled backup attempt is made and I have deleted and added something to the main drive!

Is there a way to set-up the automatic backups in ccc to delete files that have been removed from my backups, or should I be looking for another backup solution. (can superduper do this for example)

Thanks for any suggestions!