Sounds to me like you may not be looking in the right place, especially when you say "The problem is, sometimes I round out too low and then balloon and come down hard on the main wheels, or, I round out fine and then dont feel it when we start too sink towards the runway and by then its too late."
The idea, once you've rounded out and are in the process of holding off, is to look into the distance (the end of the runway is often a good guideline for how far into the distance, but this depends on the length of the runway). There is a specific point whereby, if you focus your vision on that point, your brain can easily figure out how high you are, and whether you're moving up or down relative to the runway. Someone (Chuck?) posted a very good description of this quite some time ago, including a mathematical explaination of why this works. I got lost in the maths, but it really does work - it's just that it's not something that anyone can really demonstrate how to do, you just have to learn it by yourself.
My other tip would be to read everything which anyone writes on this subject, and try it all. You might find that none of the advice works, except for one thing which one person says, and then it suddenly clicks into place.
Good luck!
FFF
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