I'm making a splitscreen game using viewport object. Game resolution is 1920x1080px, but because the splitscreen technique I can not use settings "change resolution mode" or "resize display to fill window size" so my game is allways a borderless 1920x1080 -sized window. So if someones pc's resolution is lower, the game wont fit to screen and if higher the game wont fill the whole screen.

So what would be solution to make sure game shows up right on everyones computer? I have tried Ultimate Fullscreen object but I cound not make that work in this case. One thing that of course would work, would be setting pc's resolution right before starting the game. I thought that "change resolution mode" -setting would do the trick if my first frame is 1920x1080px, but it will ruin things when going to splitscreen frame. Neither I didn't find any extension that could to do that.

Is there any good solution to this? Or is there something I'm doing wrong?...