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Is it possible to put a flag so the game starts in window mode?

I can't play in fullscreen (blackscreen) but it works in window mode but I need it forced so it starts that way, because if I use an application to do this I activate the bordeless thing after it starts and the game starts to react funny (mouse cursor position is not exact, sound disappearing, fonts aren't correctly written).

I've had this issue before with other games and I solved it by forcing bordeless window from the start rather than using a trigger after the game has already been started.
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It seems it works with Game Companion but I've barely played any to see if anything starts to happen. The cool thing is that the game (according to the official forum) isn't supposed to support widescreen natively but it seems to work at 1920x1080 for me anyway, no stretching.