I have an R9 270X, a 2560x1080 21:9 monitor, and a 1920x1080 16:9 on either side.
Radeon Software Version
I am using eyefinity in rFactor 2 with some success. My only problem is with multiview, where the image on each monitor is rendered from different angles for more realism when you have the monitors set up to wrap around you. The problem is, rFactor assumes you are using equal resolution monitors. This results in the screen breaks showing up on my center, ultrawide monitor. I have been trying to find a way to adjust this in the game with no success.
The idea I have been throwing around most recently is to set a custom resolution of 7680x1080, and overscan horizontally. rFactor would place the screen breaks 1/3 and 2/3 the distance across the span, between the monitors just where I want them. I havent been able to find a way to do this. Is it possible?