You can use at least 3 screens, but you will get a "fisheye" effect, derived from using a single camera with a very wide resolution. Essentially you need one camera for each monitor you have, and the ability to configure the size, angle and even distance from you eyes, in order to see a correct perspective inside the cockpit. This short video (using Euro Truck Simulator 2) explains it very well:I've seen people with three monitor set ups.
Guessing it "works" but isn't "perfect" ?
Well, it's not a "fix", but a patch that makes the image to look a little better. See, you can't "fix" the issue because it depends on the internal geometry of the game, and how it displays (and projects) 3D images. So, that software only tries to correct the stretching at the sides to minimize the fisheye effect on a curved screen. But it cannot make it accurately enough, simply because it cannot modify the rendering engine, so you still will see some distortion and perspective issues.It works, but yeah there is a bit of stretching. There are blending and warping software solutions that can fix the issues. Not cheap though.
Source: https://www.youtube.com/watch?v=POrg25x7jVc