I think the key to soundstage depth with the OHMS is distance from rear wall (several feet if possible) + some degree of sound reflectivity off the rear wall. The sliding glass door can work to your advantage with this but not if the speakers are too close to the wall.
Distance from rear and side walls is needed to get adequate delay for reflected sound to produce needed spatial queues for widest and deepest soundstage.
Since OHM omni sound output is attenuated by default to the rear to accomodate placement closer to walls desired by many for practical reasons, having a surface behind that refelcts the sound more can actually help to retain the needed reflected sound levels desired since the speakers are further out from the rear wall than intended and reflected sound levels lower in magnitude as a result compared to say a pure omni which will produce higher sound levels reflected from rear (and side) walls and when set up properly with distance from walls produce very deep soundstage.
This is what you would hear with a true omni like mbl set up with 5 feet or more distance from rear and side walls.
There are some good references on the internet that explains the geometry of stereo soundstage imaging and how distance from walls of 5 feet or greater in a typical set up is generally needed for best results. The listeners position in terms of distance to speakers relative to distance traveled by side and rear reflected sound is also a key factor.
Also note that the addjustments on the 5000s are useful for boosting bass levels somewhat as may often be needed when speakers are far away from walls with less bass level reinforcement. Without these adjustments, bass that sounds right closer to walls may be somewhat less if away from walls. However distance from walls is needed for the biggest and deepest soundstage. It is a dilemma. OHM does not suggest 5 feet or more distance from the rear wall. That kind of common setup as recommended is a good compromise for most in that speaks are out of the way, bass levels good, but soundstage maybe not as deep as might be, if that is something that matters to you. ITs probably a lesser consideration for most, so a reasonable solution.
FWIW, in my main rig with the 5s, I keep speaks over 5 feet out from rear wall and 4 feet or so from sides, the most possible in a fairly long and narrow room.
In my 2 channel a/v rig where the 100s reside, they are closer to the rear wall for WAF and other practical reasons in our heavily used family room. SOundstage is not as deep, but still pretty good.
