i DID notice one more little flaw of sorts that affected my 5d2 and the 6d I looked at.
Altho it appears similar to FPN, it likely is not a noise issue but a small variation in pixel performance occurring .
I'll have to post the shots when I have time to monkey with them some more but the effect is this;
A "ribbon" shaped area was affected such that when shooting SMOOTH MIDTONES there was some fine vertical banding-like structure evident. This is actually the first flaw i noticed on my 5d2 when i bought it but thought it was a noise issue at the time. If it were a normal FPN issue,the banding would have been evident over the whole range of the smooth tone area. instead, it was confined to a ribbon-like shape that meandered a bit over part of the sensor.
I managed to replicate and identify it by shooting a flat surface and enhancing the heck out of the contrast.
But it was in a real image of a foggy mountain lake at sunrise where i first found it.
So far I've only found this on the 5d2 and 6D.
I've sold my 5d2 recently, now waiting for price drop before getting a 6d, if I get one at all.