I've done some quick calculations, from 13/5/09 to today.
Using ECB and AIB SVR rates.
The tracker margin on 13/5/09 would have had to have been less than 3% before any financial loss had been incurred.
Using May 2010 as starting point, it would have had to have been less than 3.2%.
So you need to challenge that it should have been less than 3.2% by either:
A. Challenge contract - tracker should have been the rate available at drawdown.
B. 'prevailing' rate should have been the last available tracker rate.
C. If tracker had been available at the time, it should have been less than 3% margin.
Basing it in how tracker rates compared to variable / fixed rates prior to the crash is futile. There is an acknowledgement that tracker rates should never have been less than variable rates, as the borrower was receiving a guarantee for the life of the mortgage, and there was a cost to that the banks had ignored.
In 2010, in the middle of a funding crisis, I think it would have been impossible, or prohibitively expensive, for an Irish bank to be able to secure 20 or 30 year funding at a rate guaranteed to track ECB (or even Euribor). So if challenging that angle, you need to be able to calculate what the rate should have been. So you need to look at debt / cover bonds that they issued: at what rates and for what duration.
I think it would be easy to prove that 7.9% is a made up figure, but they said that's an average. But you need to prove it should have been less than 3.2%.
CBI haven't challenged the approach, so I think it's not the independent appeals panel that should be getting criticised here.