Joined transaction search wipes out some fields

I have a custom record that is a child of an Invoice.  I want to create a search for these custom records that will use the parent invoice fields as criteria and also some of the results.

As you know, Invoice has fields like Amount Paid, Amount Remaining, etc

So I have setup the criteria:
Invoice : Item on Any Line MyItem
Invoice : MainLine = true

This doesn't work, it appears you can't mix ItemOnAnyLine and MainLine - they filter each other out for some reason.

This is really limiting and makes me think I'm doing something wrong.  I mean, the strange "MainLine" filter is almost always required when you don't want to get tons of duplicate results but does this mean you also can't search for transaction with certain items on them?