According to the FBI be is 5' 8" that eleiminates him right there plus other things we probably don't know about....
C'mon "Probably don't know about" isn't good enough... there may be something but unless we know what it is, we can't eliminate on faith
The FBI's height was an initial suspect description...that doesn't mean it was accurate, even Cooper's was initially 5' 9"- 6'..
In pics with agents, he looks taller than 5' 8"...
Stack all the pieces that are consistent with Cooper.. and you hang on an unverifiable inch..