I also had your dilemma until recently. It's just a matter of training the eyes.
What you said is why you're having the problem. You said when you change your focus to the middle of the pages you no longer see the blip page, correct? (sorry if it is sumarized sort of incorrectly). Well there you go - don't look at the center of the book, look beyond it.
What I do to help is put the book at a 45 degree angle on the desk and have my eyes faceing the center of the book, but actually try to imagine the desk beyond it, or the floor below it, etc. Then you should see the blip page.
Remember though, that the blip page isn't crucial to photoreading. Just try to get a relaxed glaze and let the subconcious become aware of the text.
