i got M80's and sit about 6 ft away from them.
my ears are just about halfway between the lower tweeter and
the top midrange.
i checked to see if i was missing some h.f. by increasing the treble a little, but it was not necessary.
i guess the tweeters have a good enough off axis response downwards that a few degrees does not matter.

3 identical vertical speakers is tops.

See: http://www.blu-ray.com/community/gallery.php?member=Gelli
or: Axiom Gallery