I am the person who wrote LifeBoat. I have not tested it on a USB CD writer because I do not own one. You are the first person that I know of who has tried to use LifeBoat to burn a USB CD. So I guess you are my guinea penguin on USB CD writers.
I looked at the following link to see what is involved with writing CDs on a USB CD writer:
From what I read there I would say that CDR_DEVICE="0,0,0" should work just like it does for an IDE CD writer. If your CD writer is the first (or only) scsi device on your system then its device number is 0,0,0. If it is the second scsi device then its number is 1,0,0 and so on.
If you set the CDR_DEVICE parameter incorrectly then LifeBoat will not burn a LifeBoat CD.
I can only guess about IDESCI=. The purpose of this parameter is to tell the kernel to use the scsi modules for a device that is configured as IDE. If your USB CD writer is configured as a native scsi device then you do not need IDESCI and you should set it to null: IDESCSI= If your USB writer is configured as native IDE then you need an IDESCI parameter to tell LifeBoat which IDE device is being run as a scsi device.
The IDESCSI parameter is needed by the LifeBoat kernel at boot. If you set it incorrectly the only problem that will happen is that the LifeBoat rescue CD will not be able to write CDs, something that people rarely do in rescue mode anyway.
Also if you need the IDESCSI parameter then you also need it for your desktop kernel. You should have the parameter in your bootloader, either grub or lilo.
If you don't get LifeBoat to burn a CD on the first try or two then I suggest that you first learn to burn an ordinary ISO9660 data CD, then tell me how to do that on an USB CD writer and I could probably tell you how to make it work in LifeBoat.
In any case I would like you to let me know how things work out in detail so that I can do whatever is necessary to make LifeBoat work on USB CD.
Be prepared. Create a LifeBoat CD.