Thaun you have the exact room dimensions as our room with the exception of the ceiling height.
We're using M80s, VP150 and QS8s in a 7.1 setup ... I have our side QS8s mounted on the side walls directly to the sides of the couch (15' from front wall) and 64" off of the floor and the rear surrounds are each mounted on the rear wall 3' in from the side walls and the same distance from the floor. I actually built part of our room around the surround speakers so they end up only being 7' in back of the listening position.
I placed the speakers based on research from this and other sites suggesting speaker placement, here's Alan Loft's article...Essential Guide to Speaker Placement
from this list of very helpful articles ... The Learning Center
Just to give you an idea of how our QS8s are placed here's a shot of the back of our room ...
Good Luck and Welcome!