It's probably worth mentioning what CR OEM turbo cars run for reference. I know that VAG 1.8T 20v engines ran 9:1 or 9.5:1 from the factory depending on what car it was going in but, that would obviously be the OEM compromise on a mass produced turbo engine between reliability and drivability.

These engines a capable of reasonable power on std internals 400bhp+

I've got 1988 Renault 5 GT Turbo running a std carb blow through set up. The engine design is getting on for 50 yrs old now and that runs a std CR of 7.9:1 on it's 8v OHV non crossflow head.

The difference between the VAG engine and my old skool Renault lump is the advances in EFI technology and it's control, predominantly, ignition timing. The obvious other differences in head design have little to with a reliable CR.

Food for thought