Steam Deck 2-player Co-Op performance

[pekkamy]

Saw some good reports on https://www.protondb.com/app/2567870 the game running ok on steam deck. Its perfectly playable, just little jittery because of low fps. Tested quick and performance is ok in Training mode Solo (30+ fps). But Local multiplayer split screen with 2-players the fps is hovering 20-30 around 25 fps avg. Is there a way to boost the fps higher when using split screen co-op? I used the DirectX 11 mode to start the game. Resolution 1280x720, Windowed, vsync off. Turned everything in settings to low or off. But resolution scale 90 because I still want it look somewhat ok. Steam deck running on stable, tested GE-Proton9-11, Proton 9.0-2, Proton Experimental. Those didnt make much of a difference.
Main menu runs ok at 70+ fps with these same settings.