The DK deflectors seem to be meant to work with lowers? Are they affective without lowers? Also I've had no heat issues running fangs but 90 deg F is about the hottest you'll see where I am eh

 

2011 RKC here, and my HD Chrome Fangs push the wind OUT away from the bike a little, and the Triple Tree Bowl Deflector reduces the wind that normally comes up over the front of the tank, as it turns the air DOWN toward the engine somewhat. Think of it as reducing "Beard Lift".
Those are the 2 benefits achieved on my RKC, for those with other touring models, lowers, etc. YMMV.
Notice that with the Road Kings, you have a gap between the bottom of the windshield and the top of the headlight nacelle, it is necessary so you can unclip the windshield, push forward, and lift up to remove the windshield. This gap will always allow some leakage, however It does help with pressure adjustments to reduce the buffeting effects.
The issues above are unique to the Road Kings, and can easily be confirmed by riding your bike on a cold day at highway speed as you feel around with an ungloved hand. You will notice sizable differences before and after fangs and triple tree deflector installation. The leakage mentioned under the windshield is of little consequence, but is offered for your consideration and again, is unique to Road Kings.
Just think of your touring bike punching a hole in the wind, as a negative condition occurs at the rider, so some degree of pressure relief adds to comfort to the occupants.
Mine stay on year round, never a problem. In the Winter as I install my Reckless Fairing, they stay on then, too. The "Winter Fairing" benefit mostly is to keep the cold wind off my hands.

 

I use the DK cooling wings and those little batwing deflectors that mount on the fairing below the mirrors (I forget the proper name of them) on my 2016 Street Glide Special. I run with the vent open and I have almost 0 buffeting.

ETA: pokey074's response reminded me, I changed out my windshield to a 9" WindSplitter knock off as I am 6'2".

 

Fangs made a HUGE difference for me on my 2014 SGS. That and a 7.5" WindSplitter knockoff have completely eliminated buffeting for me.

 

I bought a set of fangs, but discovered they obscure my oval H-D engine-bar mounted lamps. So we have to make a choice!

 

I've had the "Fangs" on my 2010 103 Limited for about 6 years now.
HD says they "Don't Fit". They "Do Fit" with Hard Lowers.
I like em so much that I've never have taken them off, except for doing fork maintenance.
What I like most about the fangs is when riding in the rain, along with the hard lowers they really help keep you a lot dryer. I don't think I've stopped to put on rain pants since installing the Fangs. Also, they keep a lot of the rainwater from hitting you that used to come under the fairing. I also put a thick piece of auto door rubber trim in between the fangs and the forks to fill that 1/2 gap there.
It's been forty years since I smoke cigarettes, but if I did, running with my fairing air deflectors closed the air pocket on my EG is so calm that I could easily smoke while riding down the freeway now.
As for any additional heat caused by the less air flow from the front I run Love Jug cooling fans, which I also highly recommend.

 

14' Ultra (San Antonio, TX) I researched the hell out if this. I still wanted as much wind as possible to hit and cool the engine. My theory is that fork deflectors would take away wind from the engine.

I purchased DK Cooling Wings and did a 2in tank lift. Very little buffeting now using my 1/2 shell. Have not tested with my full face. Added benefit wind is now directed toward engine as I have wings slightly tilted up.

 

2011 SG with 10" LRS and JES fangs my shirt barley ripples

 

So we see there is a resounded confirmation that the fork deflectors, fangs, work very well. The underlying question is do the cooling wings work just as effectively by themselves, or work well in tandem with the fangs.
Also, with the fangs pushing air away from the tank, will the addition of the cooling wings point some of that air back to the motor...

At the least I think fangs are in my future

 

New question: Will the fangs improve the ride for the passenger?