First, for the purpose of full disclosure: I do have this PR course, and have studied it at least once through all the way. But I not even close to being a real "master" of this system and really want to practice more.
Also, for better or worse (as far as your problem is concerned), I inuitively already used some of these techniques and have always been a very fast reader. One of the ways I am fast, is discovered as an undergrad (for my second time in my 30's, twenty years ago), that I really almost never have to read every word. Once I liberated myself from thinking that I have to read every word, my reading speed for classes etc, more than tripled. The other, students would stay up all night studying for a test or an assignment and I would spend about an hour or less sometimes on the same material. My "secret"?
Well, no secret at all and I told them at the time: I rarely read all of it. I just learned to kind of "feel" what I was reading for--sometimes it was really to master some material, sometimes it was just to get what the teacher wanted (which was rarely the same thing).
This is a big part of the PR Whole Mind system: it is not so much about "reading", as learning. And that happens by liberating oneself from the idea that every word is important. It helps one read by kind of feeling (through the different steps and layers of the system) the important words and skipping many others.
Having said that, I can still feel your pain, so to speak, and I think part of it comes from conditioning that we all have. Fear, anxiety, and a lot of left-brained conditioning, can hinder us from reaching our full potential. So it is often not about the amount of time, or how hard we try, but "blocks" that are there from the culture, our teachers (past and present), peers, etc.
One thing that comes to mind is not to "try harder", but rather to "try easier". The problem is, THIS IS NOT SO EASY!

Or rather, it can often seem easier to say than to do.
One thing that can help is hypnosis, NLP, or tools like the Paraliminals. Writing affirmations can help. But one really has to either visualize what one writes, or really think it hard. Write at least 10 times every day: "Photoreading is easy for me. I learn and master material quickly depending on my needs."
This affirmation does not depend on preconceived (and often unrealistic) goals, such as "I will know everything in this 300 page book in the next 24 hours". That goal is usually not only unrealistic, it is often unnecessary. It is very rare in ANY kind of material, for any purpose, that you need to "know" everything in a long piece (or even a short piece) of material.
So refining purpose is key. There are often times the only purpose is to pass a test. For many classes and for many business meetings, assignments etc, this MUCH LESS, than the material that is being assigned (either by someone else or self-assigned).
This too can be addressed through meditation, hypnosis, NLP etc. Affirmations again can help. You have to write from 10-20 times every day, something along the lines of "I am excellent at pinpointing my purpose for any reading material. I know exactly what to skip, what to focus on, what to remember and what to let go of".
Again, so much of our obstacles in these areas is our own conditioning. Belief can be key. But the great thing about belief, is you can program it.
It does take some practice though.
Chunyi Lin teaches about visualizing that goes something like this: "Visualize. If you can't visualize, pretend you can. If you can't pretend, lie!"

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This is actually a very profound teaching and one that can help a lot with PR.
Don't write, or say anymore "AM I DESTINED TO BE A STUPID SLOW READER FOR THE REST OF MY LIFE?" I am sorry, but if you really want to master something as different as PR from the way most of us are taught to learn, you have to be very tough on yourself--not on how many hours or months or years you practice, as you have been doing, but rather one WHAT YOU TELL YOURSELF and what you allow your mind to dwell on.
I know this can seem difficult at first. But the good news, is if we are diligent, it really does get easier and easier.
And at first, you may have to "lie". This is only a figure of speech, but the point is, at first (and for you, I realize this no longer "at first", but the principle still applies. Maybe even more so!), it may feel like a lie.
You can no longer use any language that hints at failure. I realize that in our so-called "rational" and so-called "scientific" bias, that saying something when we (at least at first) don't believe it can feel forced or phony.
Tough.

You have to do it anyway.
What do you have to lose? Nothing! Except a few habits and ingrained ideas about "lies" and "truth".
You must keep telling yourself that PR is easy for you. That you are a fast learner and that you can master any material in whatever time you need and want for a specific purpose (again, THIS IS KEY! This is not about reading vast amounts of material just "because". It is not about being an "athlete" of reading. That is part of the "old mindset" of "speed reading" etc. This is more about mastering what YOU need for WHAT YOU NEED IT FOR. And that can often --no always-- be a LOT less than you think -- or even what the book, the boss, the teacher or whom or whatever would have you believe.
And then do the steps again. All the while telling yourself that you are getting it, that you in the state, that you are getting exactly what you need, no more and no less.
Tell yourself that you got it when you are done.
If it didn't work, you need to "lie better". The part of you that resists (and we all have this), is still saying either "this can't work! I have to read every word. There is too much to learn! Etc etc etc" Or, "This can work but not for me. I am too ...whatever"
No. This DOES work for you.
You have improved more than you realize.
You must "fool" the conscious mind. You must lead it into submission. Keep telling yourself, "I will only listen to my higher self" Tell your subconsious mind this before you go to sleep, when taking a shower, whenever you remember: "Subconsious mind, only listen to my higher self (thanks to Sonia Choquette and her book TRUST YOUR VIBES). We are learning and mastering PR!".
Don't give up! The conscious mind WILL eventually submit and go along.
Visualize. If you can't or it isn't working, tell yourself that it is. Pretend. "Lie!"

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After awhile, it will not be a "lie". You will be doing it. This is something you can do and in fact are already doing, but you just don't know it yet. Or rather you didn't. Now you do.
Anyway, I hope this helps you.
Helped me!
