I'd like any and all ideas,
After installing a light bar above the windshield, when going 64, 65 (or less if driving into the wind) the bar creates turbulence that makes the top of the cab roll and flap like a flag or like waves. Besides structural weakness, its just plain nerve racking, so for now my top speed is 63, id like to make some modification that does not include drilling a hole in the cab. Picture added.

 

What year is the truck?
One thing that might help is to look into new struts/shocks that are slightly stiffer than stock but this will affect ride quality.
The only other option I can think of is possibly moving the light bar slightly to see if that changes anything as sometimes moving something even 1” can cause a big difference.
Other than that I’m not to sure as it might be best to just sell this setup and look into other light bar options as these trucks have a lot of mounting options for light bars.

 

i got rid of my lightbar, which the same mounts, due to wind noise. the only thing that anyone ever reported having success with was putting a plastic tube over the bar to change the aerodynamics of the flow. looked like crap to me.

 

I have one mounted on my bull bar. I do not notice any wind noise from it. I would mount it in front of the truck.

 

Some duct tape racing stripes might reinforce the flappy roof, maybe a checkorboard pattern of duct tape would make it like a carbon fiber weave.

 

Extend the tape to the top of the light bar. This will help keep it warm. It is getting cold and trying to tell you.

 

Never understood mounting lightbars on these crappy mounts that are bolted/riveted into the A pillars. Drilling into the A pillars really weakens the structure of the cab, which the OP is experiencing. Not to mention the wind noise by mounting a brick on your truck right at your head.

Best place to mount a lightbar is on the back of the cab. I have mine mounted on a BackRack. No wind noise, no structural damage, and no vibrating/fluttering light.

AK4wheeler

 

Nice. Mounted mine behind the grill

 

You can't tell by the picture (or maybe you can) but the light bar is curved to match the curve of the windshield, my first thought was to move it to the bar behind the cab, I have a winch and fog lights on the front bar, but its to curved for that. Moving the projection up or down make only a few mph difference, I'm going to try 2 or 3 pieces of flashing about 6" x 3" bent 90° and attach them to the fins or stagger them under it on the cab and see which placement and angle works best, if it doesn't work 🤔 it'll be the next person's headache. I will warn them of course.

 

I did say any and all ideas.