Изменить стиль окна в форме посредством WinApi

        [DllImport("user32.dll", SetLastError = true)]
        internal static extern bool SetWindowPos(IntPtr hWnd, IntPtr hWndInsertAfter, int X, int Y, int cx, int cy, SetWindowPosFlags uFlags);
        [DllImport("user32.dll", SetLastError = true)]
        internal static extern IntPtr SetParent(IntPtr hWndChild, IntPtr hWndNewParent);
        [DllImport("user32.dll", SetLastError = true)]
        internal static extern IntPtr FindWindow(IntPtr ZeroOnly, string lpWindowName);
        [DllImport("user32.dll", EntryPoint = "SetWindowLong")]
        private static extern int SetWindowLong32(HandleRef hWnd, int nIndex, int dwNewLong);
 
        [DllImport("user32.dll", EntryPoint = "SetWindowLongPtr")]
        private static extern IntPtr SetWindowLongPtr64(HandleRef hWnd, int nIndex, IntPtr dwNewLong);
 
        public static IntPtr SetWindowLongPtr(HandleRef hWnd, int nIndex, IntPtr dwNewLong)
        {
            if (IntPtr.Size == 8)
                return SetWindowLongPtr64(hWnd, nIndex, dwNewLong);
            else
                return new IntPtr(SetWindowLong32(hWnd, nIndex, dwNewLong.ToInt32()));
        }

  Process p = Process.Start(path);
                Thread.Sleep(500);
                //  p.WaitForInputIdle();
                this.WindowState = FormWindowState.Maximized;
 
                WinAPI.SetWindowPos(p.MainWindowHandle, this.Handle, 0, 0, 1920, 1080, WinAPI.SetWindowPosFlags.DrawFrame | WinAPI.SetWindowPosFlags.ShowWindow);
                WinAPI.SetParent(p.MainWindowHandle, this.Handle);
                WinAPI.SetWindowLongPtr(new HandleRef(this, p.MainWindowHandle), -16, new IntPtr(0x01000000));