'07 ultra classic, recently started vibrating windshield . It's a 6.5" Klockwerks that has been on for awhile. seems to be around 2500-3000 rpm. Inner fairing supports are good, inner & outter fairng halves are secured tightly together. Could windshield be tightened too much? could the exhaust be causing bad harmonics? thanks in advance.

 

Does the vibration show anywhere else? How is the mileage on front tire? Lotsa variables that could be possible.Doubt that the shield can really be over-tightened that much, because those three little brass-into-plastic inserts won't take a whole lot of torque without damage.If in doubt,put a torque wrench on the fasteners. Careful though, you're only looking at 6 to 13 INCH-POUNDS. That's not much.

 

Probably a worn Front engine mount...

 

I'm in there with Musician. Maybe the nutserts for the windshield are stripped? You said you checked the two supports for the inner, but did you remove the fairing completely and look close? Typically they'll break at the upper section at the bend. You also looked at the support arms that extend out to the speaker grills? Any windshield bags fastened? I took mine off due to too much shaking.
Let us know what you find.