The extra hole increases bass slightly, but doesn't do much for soundstage I'm afraid. I didn't take any pics of the second build, but the hole was located just slightly above centre of the cups, which would make it roughly centre relative to the driver. In yours there's a single piece of foam across the back of the cup through, so you wouldn't be able to drill through without pulling the hole in the foam as well. In the second build I merely split the foam into two halves.
I think the limitations to the soundstage are inherent to just the size of the cups. The outer edges of the cups literally make contact with the edge of the drivers, so the only cup space is due to the angle of the cups themselves. In that, I put in the foam and some damping just to cut out the treble reflections.
One thing you can try is to take out the piece of felt that's under the pad. I'm particularly sensitive to treble so I almost always use something as a filter. Taking that out should bring up the top end and possibly add to the sense of space.