Thats not really how compound turbo works, the large turbo is connected to the exhaust stream of the engine and small turbos. Therefore the large turbo isnt seeing an NA 3L v6 engine feeding it exhaust but an already turbocharged engine. Kevin Jewer in the states runs 7s on his setup and spools a GT45R sized turbo before 5000rpm on a 2L motor, because the pressure ratio of the small turbos allows a kind of artificial displacement increase. Id be fairly happy with full boost from the large turbo at 5000rpm simply due to the fact that thats where the boost and power fell off on the dyno. With the external wastegates the car holds 20+psi to redline compared to 14 before, so an extra kick in the guts from the GT42R should be enough to get me into the 10s and if not.... we still have the blue bottle hooked up!