no need for modding that my friend
- this thing was implemented long time ago by TDW in his UIs so is already in magnum opus.
When you are using the attack periscope (for example) if you look in the left side of the screen you will see an icon where is writted ,,HUD'' - under the ,,RAOFB,, icon - there you must to click and play with it.
P.S. if you can not manage to find that let me know and i will post a picture for you
Salute