My apologies I misread what you said. I largely agree with you. I believe the claim that NAA installed backfire screens originated with Schmued. He wasn't actually involved with the F-82 project at that time. He claimed Forrestal intervened on GM's behalf. Regardless of the details backfire screens will only prevent backfires from damaging the intake. They will not prevent the actual backfires or othe mechanical problems they can cause..
Why do you think that Schmued 'wasn't actually involved' with the F-82 project. True the F-86 was in full bore when the XP-82 first flew but he was involved.
The simple and cheap interim solution was to limit the G6 to power levels (60in @ 3200rpm) that the intake manifold could safely tolerate backfiring and research why the F-82 specifically. It's important to point out that this backfire problem was exclusive to the F-82. No other aircraft fitted with a two-stage Allison experienced this problem.
NAA had so many issues with the XP-51J that they quit testing it. The only reason they agreed to build one was a AAF/NAA/Allison conference at Wright in which Allison practically begged AAF to fund the project.
Your simple 'solution' re: Allison limitations to Boost, eliminated the performance envelope top half and emasculated the Merlin driven P-82. Equivalent to Steve Hinton deciding to use 110/LL in Voodoo.
This includes the Allison's XP-51J test mules that were refitted with G6 prototypes. It took about two years to sort out and remedy the problem.
Wow, now there is a solution - take an airframe with 470+mph top speed and reduce it to 440 because you (Allison) once again can't meet performance specifications tied to the contract. Dramatically reduce the performance - and by definition its combat potential - because your design and executive team can't deliver?
The truth is that the F-82 was largely obsolescent the moment it entered production and the USAF did not want to spend more than the minimum necessary.