i use silicone and never had a problem.

 

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I put a visor on my '96 when it was weeks old. Sucked drilling holes in a brand new $28k truck but I really liked the way they looked. I used ss screws and plenty of clear silicone. I had one on another truck, too, installed the same way, and both visors have been off numerous times for windshield replacements and never had any leak, rust, rot etc. Going on 20 years here in the rust belt.

My only really negative to adding a visor would be the loss of mpg. If you want to get good mileage don't put one on. I lost at least 2 mpg on the highway.

 

I do like the look of a visor especially when a complimentary bed fairing is added.

Our state allows tint along the top of the windshield. I have this on mine and find that it is helpful as the sun starts to set.