Sorry for such a late response...
I finally got them mounted, though.
I tried a bunch of temporary positions.
The tweeters sounded best on the dash, reflecting of the windshield.
Second best was on axis mounted in the 'shark-fins'.
Third best was off-axis next to the mid drivers, essentially sounding like they were mounted coaxially.
Fourth and fifth best were where the headliner meets the windshield in the corners and on axis in the kick panels.
After all the testing, I decided to flush mount the tweeters in the doors, directly next to the mids. The soundstage is a little lower than I wanted, but it eliminated the ability to localize the tweeter and it was one of the easier options. With the tweeters flush-mounted and color-matched, it looks stock as well, so I am happy.
I'll post up some pics or a link to some when I get a chance.