Hey mrpkd- this is Ben, you emailed me yesterday. I found some time to figure out a fix for you. Figured I would post my sucess here so others can easily do this also.
Modifying or repacking ISO images can sometimes be tricky. I usually do not like messing with them and really haven't much in the past. Also, easy software to use to do this usually costs!
I searched for ISO modifying software and found MagicISO. The trial version is limited but you can accomplish what you need. Here is a link for their site:
Download and install it. Navigate to the ISO image in the bottom window. When you double click the ISO, it's contents will be in the top window. Now navigate to the location where the file is. Create a new startup.bat on your desktop. Drag and drop that into the top window. You will be prompted if you want to overwrite or add the file. Then close MagicISO, you will be prompted again if you want to save, of course you want to.
Now just burn your ISO and it will work for you. Those steps are the ones I did and I have Filelink running right now with my new CD on one of my backup systems.