Yeah the 11 works OK but the 10 probably is the right line an the 9/10 atlantis. The 9 works OK as well on the 9/10 atlantis but things have to be just right.
The 9/10 atlantis is not as strong on the butt as the echos so you would probably find the 7wt to be OK and it should handle most stripers. Definitely stronger than the 11' 7 T&T.
However the 8wt echo might not be a bad choice if it really works well with the 10wt outbound like RIOs charts suggest. Then you would be right in line with what the 9/10 atlantis throws. I have the 9 echo but have only used it so far with the 9 delta spey line and have not ran any outbounds through it. The 8wt would also give you a little more oomph for when you catch that 40 pounder.