I found this bit about closing your eyes curious. It doesn't matter for my mental imagery if my eyes are closed or not. My eyelids are not a movie screen. I can imagine things quite as well with my eyes open. I focus less on what my eyes are seeing when I think hard about mental images, but they aren't really in competition. It's very easy to imagine visual things right there in my actual eye imagery.
Another article that touches on this in a different way is temple grandin's paper on how animals think