STOGEMightyNo. Its because for the normal method, you have to replace the original mumble_ol.dll with a custom one.
I just made a mumble overlay guide for DirtyBomb so I have all this useless knowledge about them stuck in my head.
What you're realistically doing when you install a Mumble overlay crosshair is* Making Mumble use the default overlay
* Removing the names of people talking and centering the default smiley face thingy in the center of the screen.
* Replacing said smiley face with a crosshair of your choosing and adding the functionality of pressing "Insert" to turn it on/off
So, if you really wanted to you could have the smiley face as a crosshair and it'd serve the exact same purpose and be completely fine as all you're using is a mumble overlay that removes the names - Not replacing any files.
Even then the file replacing you're doing is for Mumble anyway, how can a game detect that? Not to mention Mumble is white listed by pretty much every game ever as it's a voice communications program.
Furthermore some gaming monitors (including the one I have) come with a crosshair function built in, I just don't like any of the crosshairs provided to use the function, so I turn to mumble overlays.
In the end though, I don't think mumble overlay crosshairs are really that viable for TF2, I mean your choice of crosshair is pretty vast, the reason I targeted DirtyBomb with my guide was because it has literally two crosshair options ingame, one of which isn't even static.
Thats the second method.
Thanks for showing us.
http://ozfortress.com/showthread.php?t=63309