Hi Dave,
I'm sorry for the lack of response until now...
As you have already worked out the version of the xml cable configuration file you will need to edit is the one that gets placed in the add ins folder after it is installed (or you could edit it in the download xml file before you install the addin. The xml file gets copied to a weird location. The best way of finding it is to look in the log file window (on the toolbar, last tool on the right). Using this tool look for the following highlighted line on your system equivalent (you will need to start editing and bring up the cable configuration window to get to this point in the log)."
[ATTACH=CONFIG]21533[/ATTACH]
On the other point of having different #s of fibers per tube, the tools unfortunately do not support this type of configuration at this time.
Again sorry for the lack of response in getting back to you.
mark