It sounds okay, could be worse.
With that said - it looks fast. I think that's what matters most - no? Either way, it's coming along nicely. Surely the end product will sound better/different.
And as far as the redline goes - no way it can be more than 7k or so (based on this latest video). Maybe 7.2-7.3k if we're lucky.
2017 F80 M3 ZCP Atlantis Blue Metallic on Silverstone full interior