Thanks for all your comments.

The following is my desctop assessment - I have no first hand experience with the solutions I discuss (but I have spendt many hours researching and discussing in many channels). I recognize that I generalize and that mileage will vary greatly depending on tastes, needs, type of bike, other bike mods, etc, etc. Take it for what it is worth - I am no expert in this field.

1. Clip Ons work decent enough - a first go to solution for dealing with air flow problems. It is inexpensive, quick and dirty, and often delivers more than adequate results. If it doesn't, it could likely still be used in combination with an upgraded main screen for a combined effect. And unlike a tall fixed screen, it can be removed off road (for best possible visibility as well as added safety against getting your face and neck cut up in the event of a crash).
2. Shy away from center mounted clip ons - this as they block view where it counts the most - beter with two mounts, one at either side of the screen
3. Adjustability: up, down, inwards and outwards, plus tilt - is the way to go in pursuit of optimal wind deflection. It might not look as good though, and will cost more.
4. Heed warnings - take the damn thing off when riding offroad. Not only for better visibility, but to avoid planting your face onto it - especially when standing up
5. Having an adjustable main screen in place, or in addtion to a clip on, might deliver the best results and convenience (more on that on a bit)
6. MRA, Puig, Powerbronze - are great options for the T7 - both for screens and deflectors (more on that in a bit).
7. Acrylic is the way to go, even it is far more brittle than polycarbonate, and therefore brakes easier. But, it is far more scratch resistant, it doesn't yellow, and you can buff out scratches easy.
8. You want screen thickness to be at least 3 mm, preferably 4mm, especially if you go for acrylic (3mm seems to be the standard)
9. Clip Ons don't really get stolen all that often

Adjustable brackets for main screen
On e-bay, and a thousand other places, you can find brackets enabling you to elevate your stock screen - without the use of tools. The solution does however leave a large gap at the bottom when the screen is at the elevated position. Some report that this can cause the air bubble to collapse, cause more turbulance (or in worse ways), and can also reduce the height above the screen which the air gets directed. Some report changes in turbulance causing rain to actually be pushed downwards - into everything from through helmet opening, and/or down the front of the neck (soaking you from the inside out), or pooling up at the crotch and seat - all leaving the rider miserable. Others report wonderful results.

In my opinion, I really just don't like how they make the bike look, especially with the screen elevated. It looks like a hack job to me.

MRA
MRA offers an adjustable main screen for some bike models that is simply awesome. Not only is it easy to operate, but it doesn't leave the large gap at the bottom end which a lot of other solutions does.

The contours of MRA screens, looks to me to be more technically advanced than most other options out there. Most other options lack a lip/spolier contour at top, which helps blast the wind high (a tried and tested concept by bike manufacturers for a very long time). Most others have a straight vertical contour with no lip - which to some may look more sleek, and which probably is simpler to manufacture (cheaper). Hondas, Yamahas and BMW's alike would often have this lip on many adventure and offroad bikes with short screens. Maybe that is why many don't offer the look anymore - because it looks to 90's (forgetting that it offerred some performance improvements - atleast on those bikes that aimed to get it right in the 90*s simply didn't just add them to make the bike look modern?).

Sadly MRA doesn't offer an adjustable main screen for the Tenere 700 - only fixed screens and a clip on defelctor. They do however offer adjustable brackets similar to those that you can find on fleabay. If I was to go down this rout (which I won't, for the reasons mentioned above), I would simply use my stock screen and buy cheap brackets from wherever.

The fixed screens from MRA looks awesome, but the added length would not be desireable offroad (heeding Tim Cullins's warnings).

MRA does in my opinion offer the best clip on technology, with every desireable adjustment and the easiest operation of the lot. If I am to get a clip on for my T7, it will probably be an MRA.

The MRA has in my opinion the better looking screens - or does Powerbronze? I can't decide. I like the sleek straight and modern look of Powerbronze, but I also like the more technical contoured look of the MRA. The MRA contoured lip looks more 90's or early 2000, wheras the straight looks more futuristic. The first looks more functional, the latter just... "looks". The MRA screens seem to have kept the original design of the bike in mind - not going too crazy. The same goes for PowerBronze.

PowerBronze
Offers an adjustable screen for the T7 (and more adventure bikes than the other manufacturers - or so it seems). Their screens look sexy, retaining the original look of the bike - atleast the T7.

Their adjustment mechanism doesn't seem as easy to operate as the ones from MRA. But, if MRA doesn't have an adjustable screen for your bike, then Powerbronze might your best choice. The same goes for their clip on deflectors.

With the adjustable screen from PB, you can keep your screen low off road, and elevate it when you cruise at high speeds - without leaving a huge gap at the bottom. Combined with a removable clip on for added height and improved deflection - this might offer the best of all worlds. Personally I would conscider getting the main screen from PB and the deflector from MRA (unless MRA should soon produce an adjustable screen for the T7, upon which I would likely get both from MRA).

Puig
Puig seems to provide awesome and good looking kits. But in my opinion, Powerbronze and MRA has it beat by a smidgeon.

Madstad
Has a decent kit, with a look that I can't say if I hate or love - it deviates too much from the original design of my T7, without adding anny real technical advances relative to the competition - not as far as I can see anyways.

My likely choice
I'm leaning towards getting a clip on from MRA and see how far it takes me. If not enough, I will likely get an adjustable screen from PowerBronze and see how far that takes me (with or without the combined effect of the MRA). If that doen't do the job, I will likely get a fixed touring screen from MRA in combination with the clip on. It will surely add more height than I like, but I will allways have the option to switch back to the original screen for trips where it is especially important to have the lower screen.

__________________
Blog: www.bamakobyvespa.no
My Youtube Channel