Change splitscreen layout ingame

Hey,

We are making a 4 player splitscreen game at the moment.
At the end of the game I would like to transition from the 4 player splitscreen to fullscreen.
To achieve this I tried to change the size of the splitscreen of the first player.

I tried this:

UGameViewportClient* Viewport = GetWorld()->GetGameViewport();

FSplitscreenData SplitData = Viewport->SplitscreenInfo[Viewport->GetCurrentSplitscreenConfiguration()];
UE_LOG(LogClass, Log, TEXT("LocalPlayerX: %f"), SplitData.PlayerData[0].SizeX);
UE_LOG(LogClass, Log, TEXT("LocalPlayerY: %f"), SplitData.PlayerData[0].SizeY);

SplitData.PlayerData[0].SizeX = FMath::Lerp(LocalPlayer->Size.X, 1.f, DeltaSeconds);
SplitData.PlayerData[0].SizeY = FMath::Lerp(LocalPlayer->Size.Y, 1.f, DeltaSeconds);

Viewport->SplitscreenInfo[Viewport->GetCurrentSplitscreenConfiguration()] = SplitData;

This code works without errors but if the splitscreen is not the default layout the screen is just black.
Is there anyway to change the default splitscreen layout without the screen turning black?
I would also appreciate source code change tips.

Thanks for your answers