I have a 2015 DL650 with the Suzuki vario touring windshield. I was thinking of replacing the adjustable top portion with a MRA X-Screen bolt-on. Would I be able to bolt on the X-Screen using the existing holes in the main lower portion of the existing windshield? Can anyone share their installation experience with this kind of swap?
No, you won't be able to use the holes already in the screen. Completely different mounting platform between the two designs.
You might get some better air control with the wider X Creen, and if you use the dog-bone extensions you can get the air blast up over you a bit better.
Since buying an x Creen is expensive, just to experiment with, consider removing your current adjustable part of the factory Vario and making a bigger piece out of acrylic. You can cut with an abrasive cut off wheel or fine tooth jigsaw. Be careful about drilling, unless it is polycarbonate you must use one the "step drills" that look like a pine cone. These have one cutting edge and won't crack the acrylic like a normal drill bit.