All jokes aside.
Bar risers are bad idea on any sporty type bike including dirt bikes so you should know this. (most common beginners mistake on dirt bikes including me)
It messes with the riding dynamics, the geometry and weight distribution, especially if you also move the bars further back.
KTM in general, both dirt and road, benefit from a bit of weight over the front during turning, just the way they are build.
On the other hand why anyone wants to sit up more on an SDR 1290 is beyond me, the wind pressure and neck strain is bad enough at legal speed to want to tuck in a bit more.
I'm reasonably tall and can't see any benefit from raising the bars on this bike, it is very comfortable for longer rides.
If you have issues with your back I would suggest (in the nicest possible way without being condescending) to look at your body position.
The arms are not supposed to take the weight of your body, use the knees to grip the frame and support your torso with your legs (strongest muscles in the body).
At normal speeds there is enough wind pressure on the front of your body to have no strain at all on back and arms.
Please get rid of these awful things or buy a beemer RT or so!