Here's a hypothetical for anyone who has the knowledge to consider with "record-breaking" implications. I'm doing some research on what would be required to "operate" a GTSIO-520-H at 60,000 ft with a two-stage turbocharging system. Automotive turbos are OKAY and I'd like to have ~120 HP at altitude at 2700 RPM. The numbers I've run so far put me at about an 8:1 overall pressure ratio (after efficiency and intercooler losses) but I haven't been able to find anyone locally with enough aircraft turbocharging knowledge to pitch in. Thoughts?