Bigwill, any type of speaker can be used in any configuration for surround speakers.
I had the opportunity to try out M22s vs. QS8s as surround in both the side and behind positions.
The link to my thoughts on this can be found
here in this old post.
I have yet to place my VP150 in the rear as my siixth channel but it has been done as well by others.
The
suggestions for surrounds are usually placing them first (one pair) on the wall, to the sides, slightly forward and above.
As for the back rears, i would say slightly above but potentially angled if they are direct radiating as opposed to the multidirectional style.
I personally feel the multidirectional speakers are WAY easier to place but certainly direct speakers can be equally as effective with some tweaking.
Using all VP100s for side and rear surrounds actually sounds quite interesting.
