You have done your home work..!
Parts fit is so critical that it is not realistic for any mass producer to make every unit a world class engine. If you have access to bins full of parts plus have machinist skills, time to kill and know what feels right...then you can make these engines really scream.
I could tear down the same engine to the bare case and reassemble it with the same parts and get different results every time.
The best one I ever had was a .061 that Bill used at a FAI meet in Germany to place 3rd. That one would rev a 4.2 x 4 to 42,000. It had a Satanic howl to it. It died from too much prop, too much nitro, too much static compression ratio and no way to richen it after it got it's first gulp of air.
At this level of performance, component failure is to be expected but failure can be delayed with cautious use of prop load, compression and nitro %. Bill and the guys at N.A.S.S. have already burned through much time and money playing with these things so if you invest some of your time to pick their brains they can save you some grief.