Finally got my last piece of the puzzle. A pair of SQ8's for the back surrounds were shipped same day and arrived the morning after (!). I had to spend half a night getting the wires through the wall and into the ceiling. Yet another one of my mistakes - I had the wires terminated at ankle hight and that is not where you hang the back surrounds . I thought about bookshelves on stands when planning.
I could not yet test the sound in full 7.1 - did not want to wake up the family at 3am with that imperial star destroyer fly by from the back, but even at 1% of the volume it was interesting.
Volume test on the reciever now sounds same from all the 4 surrounds (my old HTIB speakers were hissing considerably higher than QS8's).
I will post my impressions when I am back home for the long weekend.

M60 x 2
QS8 x 4
VP150
HSU STF2
Panasonic LT500U
Marantz 7400
Panasonic DVD-F87