I personally do not believe CE 399 was "planted".
The damage to the windshield and the windshield chrome strip of the limo came from bullet lead, likely from the bullet that shattered JFK's head at Z312/Z313.
I do believe we are making some progress here.
Since you don't believe 399 was planted, then how do you suppose it was found at Parkland ?
It certainly didn't fall off of JFK's gurney as that gurney was still in the trauma room that JFK was cooling off on.
Therefore, we know by the process of elimination that 399 must have been the bullet that wounded JBC. How else could it have gotten there ?
That wasn't hard was it ?
Now, let's deal with JFK's back/throat wound.
Since we know that no bullet was found in JFK's neck, we know that the throat wound had to be an exit wound.
We know this by the process of elimination. Since there is no exit wound for a bullet entering JFK's throat, and no bullet found in his neck, the inescapable conclusion is that the bullet which struck him in the back had to have exited through his throat, causing that wound.
This isn't speculation, it's fact.
So now we have established that a bullet entered JFK's back, passed through him, and exited his throat.
Next, we must ask what happened to the bullet that passed throught JFK.
Since there is no bullet found in the limo, we must conclude that the bullet that passed through JFK, went on to wound JBC, and was the one recovered at Parkland, CE399.
How else could it have happened ?
As I've said before, the application of a little common sense and logical deductive reasoning is all that's necessary to arrive at the SINGLE BULLET FACT.