You are correct, The directions want you to stick the bumpers to the hood. But I stuck them to the back of the shield instead of the hood. It accomplishes the same intent on the off chance that the shield does flex, and it avoids putting the sticky on the paint. Win, win. Not sure why the directions recommend otherwise to start with.
I did the same thing on the deflector on my Tahoe and it was fine that way for 10 years.
Here are a few pics of the process of the install...
Most importantly "no more hood chips".