External or internal?
Remember that to Chameleon, the drive it is installed on is always the first drive.
It doesn't matter:
What you see when doing diskutil list in Terminal
In what order your drives are plugged in
How your drives are configured in the BIOS.
For those reasons you might need to experiment for a while with disk/volume identifiers until you manage to hide the right drive or partition.
If it's an external drive which doesn't retain the same disk or volume identifier over time, you can hide it by UUID instead of disk identifier. I believe you can see its UUID in Disk Utility, I'm not sure exactly, I've never used this feature myself.
Read boothelp.txt for more infomation, follow the link to the guide in my signature to get it.