So what exact limiters are you modifying, and what are you doing to those modifiers? I looked at the 2014 GT 5.0 vs the 2014 GT 5.0 with Roush TVS and it seems like they reduced the amount of spark advance in the temperature adders, and re-scaled the BKT tables for load while increasing the spark by a few degrees. We have pretty much the same spark tables.
At WOT, the spark is essentially the same from 4000-6000 RPM. The way the SHO's transmission/final drive is set up and the engine's powerband, it basically hits 6000 RPM for the 1-2 (and I try to target 6k RPM for the shifts), and then never drops below 4500 RPM after the shifts. The load stays the same, about 1.7-1.8, making it simple to identify in the BKT cells. I experimented with higher shift RPMs but it seems like the car loses momentum and the turbochargers are just pumping around heat.
My MBT's are pretty much set to 30-35+ degrees of advance in those cells. I don't normally see any knock retard with 1 heat range colder plugs. Borderline maxes out around 9-11 degrees of advance in those cells. I tried adding up to 6*-7* of timing to the BKT, and almost all of it was pulled as knock retard.