I don't, there's a large Google Music cache plus a lot of downloaded game data (e.g. Gameloft) so there's only 2-3GB free, maybe enough to include a 'normal' data image but not sdcard too.
What are people doing in this scenario?
Is there an option in Clockworkmod that I've missed?
Or is there a way to get it to backup to a real SD card via USB-OTG? (I tried the mount USB item but it errored)