Here is a quick tutorial on how to make LU windowed mode better. To get rid of those nasty borders and fix the window position we are going use a program called Windowed Borderless Gaming which you can get here. (http://westechsolutions.net/sites/WindowedBorderlessGaming/download) With this same program we will also prevent the cursor from going over the game window.
1. Download the program mentioned above, unpack it and run the exe.
Note: this is a portable app and requires no installation so you can just drop the folder everywhere you like the most.
Once opened you'll see this:
(https://snag.gy/Mixq3m.jpg)
2. Now open LU browser, enable the windowed mode by ticking the box in Tools>Settings if you didn't already and connect to any server to start the game.
3. Open the program's context menu by clicking its tray icon and select Add window ( F3 ). Go back to the game and press F3. If you did everything correctly you will get this message:
(https://snag.gy/ZcOAMn.jpg)
Note: when I did this process my game crashed however the program registers everything correctly so in case it happens, start the game again and continue with the next point.
4. Now that the program keeps track of the game let's proceed to adjust its settings, so open the context menu and select Settings>Game settings.
(https://snag.gy/DiFY0t.jpg)
This is how it should look like by default.
5. To get rid of the borders we are going to move the game window a bit up and left, so start decreasing the X and Y offsets clicking Apply to see the changes, until the borders are completely hidden. What worked best for me is X: -3 and Y: -25.
6. To prevent the mouse from going over the game window, check Manage mouse and Lock to game window options.
We are done!
Moreover the program will recognise everytime you start the game and instantly apply the settings you previously defined, else once in game press F4 (by default) to apply the settings. Also don't forget to check Run at startup to avoid the hassle of opening it everytime you turn on your PC.