Webley,
I have received 3 Sony G400s and 1 P991. All of them have this problem, more or less. So I suppose all trinitron tube has potential problem of focus(convengence, actually). And they do not provide Area Adjustment.
On the sony I currently have, I found that the top screen needs Convengence 48, while the bottem needs 60. So I compromised 55.
However, on this P991, the top needs 38 and the bottom needs 70!!!! It can not be tolerated so that it's going back. Dell's return is nice though.
I don't know if all P991s are like that. But it's not supposed to. I am tired monitor-exchanging. So I decided to keep the final Sony and return P991. I bought the Sony from Gateway for 450$. Now it's time to PM with Dell's 20% off using my AMEX.