U want zero leg? Go twins over stock blower u will have the biggest smile on your face...
There are trade-offs in any set-up. In this configuration, there's benefit at the low end but the SC becomes a liability on the high-end - adding increased heat to the charge and dragging HP from the engine. In Heffner's early experience with one of Ray's first TT cars, he experimented with this set-up and eventually discarded it in favor of TT-only. Subsequent to that, Hennessey offered that configuration and allegedly has some very happy clients with it.
My preference is for a properly set-up TT system. To the op, I think that graph indicates that there is a LOT of room for improvement. On the high-end, I thing you should be seeing 80-100HP more than is shown. More importantly, there is a lot of turbo-lag shown in that graph. I think there are areas in the low range where you can/should be making SUBSTANTIALLY more power - all of which would contribute to an entirely different driving characteristic. It is important, as you say, to get the right turbos but also as important is sizing the tubing in front of the turbos. Finally, making sure you have good wastegates (with no leakage) and pay attention to the exhaust tubing post-turbos. A/F's look acceptable if not good with just one area where the car is coming onto boost that is OK but should be watched.
