Attachment node field vs. file fields in a content view Sorry, can't think of a better title...

I've created a content view for a specific content type where each node has lots of attached files in one 'attachment'' field.

I want a table of files with columns for file description and file size, grouped by node title.

This is (almost) fine if I use the Nodes 'attachment' field, giving me a list of files (one per row) with the file name or (even better) the file's description.

However, if I want the file size, I create a relationship to File Usage, but this creates a combinatorial explosion in the number of results, returning one file size per file linked to the node per file row...

If I remove the attachment field, just getting the file name and size, its fine. But I want the file description and the size. 

The thing is the description seems to be a node property but the size is a file property and the relationship is at the node level, not the file level.
If I drop the relationship, I found that changing the file formatter to 'table of files' shows the size column. Magic. Gives me 98% of what I want, so I'm happy enough.