I bet we could alter the boxes to show up, but the only problem is that we don't know where the "switch" is located? Could it be menu_1024_768.ini? Probably not, but it's worth a look.
As of now, I don't use any weak spot guide, but if you could mod it so that it happens, I am 100% sure that I would use it!
And no, it is not always possible to aim
correctly at these weak spots without the AI help.
In the end, what it really comes down to is this:
-how good of a sniper/mathematician/perfectionist you are.
-the distance between you and the target.
-if the target is turning or taking evasive actions.
With or without a weak spot guide, you may or may not be able to hit your intended target...
...But it
is possible