I think you mostly have the right information, but there might be something you're missing if it's not being drawn to your attention, but first the FAQ:
In your situation if you're trying to add another 400 nodes (for example) and you're including volumes, the Discovery may not complete.
When you get to those pages in the Discovery, make sure you're not selecting any volumes (or interfaces if you've hit that limit as well) and continue on.
It may or may not tell you that it failed to add the nodes and why, but that's something I've seen in a smaller QA environment we have.
I was going to recommend re-checking for A and D drives (default for floppy and disk), but it looks like you've addressed that in your post.