I had the same issue with my car. After about 65 mph, I could see it move/vibrate if I looked at the edges of where the hood and fender meet. It took a lot of playing around with the rubber stops, but I finally got it right. The key is to balance getting the hood level with the lines on the car, and getting it to close securely enough that it doesn't vibrate or move.
I first I turned the rubber stops so that they were higher, which cured the problem, but the hood wasn't level from front to back in relation to the fender. I actually screwed them back down, past where they originally were, and that solved it. I think that a lot of my actual problem was that the four rubber stops weren't adjusted to each other. You can't just screw them all down to the exact same measurement, because there are other factors that somehow change how the hood sits. It's a good starting point though. I started by screwing them all about half way down, then closed the hood to see how it matched up with the fenders. I also tried to wiggle the hood to see if the stops were doing their job and keeping it secure. After making a couple of minor adjustments, I took it out on the hwy and tested it. When driving it, you can see how much it moves and where. I noticed that if it the majority of the hood moved, then all of the rubber stops needed to be higher. When I got that tweaked, it just vibrated slightly on the driver's side. I turned the rubber stop on the driver's side just slightly, and no more problems.
It helps if you have someone sit in the passenger seat so that they can see how that side of the hood is doing. From the driver's seat, you can't see the lines of the car and how the fender and hood match up. I didn't even know that side needed adjusting until I was complaining about fixing the driver's side, and my wife commented that the passenger side did the same thing.