This script requires GTALua.
You can download it here: http://www.gtalua.com/

Description
This script will allow you to lock your wanted level,
there is already one of this sort of script on but its very lacking,
if you press U on your keyboard with this mod it opens a menu
where you can choose on what star you want to lock it to.

Controls
U -- Open menu
Numpad 5 -- Select option
Numpad 8 -- Up
Numpad 2 -- Down
Back button -- Close menu

Installation guide
Put the folder: Lock Wanted Level into your GTALua/Addons folder
and put 8V.SFV in your main gta v directory root folder
then start the game and press U.