Lets Talk Raising the 1.6 EcoBoost Redline

[Magnetic]

When planning my engine build and looking over dyno sheets I keep running into issues with the turbo sizing being a little too big or a little too small. With a GT2560 power comes on early but you have the same issue as stock that it starts to die off towards redline (its also not quite big enough for really big numbers). Alternately, the GTX2860R keeps strong power all the way up to redline but shifting will always bring you below peak boost since that usually happens just over 5000RPM. My solution (which is no surprise seeing as I've always been a Honda guy till now) is to build the engine to have a safe higher RPM. Allowing the engine to rev safely to somewhere around 8000-8500RPM would allow for a lager turbo size where you could stay in full boost all the way through the gears.

So after all that preamble the topic of discussion, and my question is, which parts begin to give out or not operate properly at higher RPMs. The engine already has an under-square bore/stroke ratio and a low rotating mass, so it seems like a properly built engine should be able to absolutely scream. Which Internals do I need to watch out for and make sure to upgrade during a build? Who has mechanically over revved their FiST and broken something? What broke?

Also feel entirely free to tell me this is a silly question and I shouldn't even worry about it.

I'm curious to know as well. I'd like to get a motor built that does 9K RPM. (Next year)