Another way to twincharge would be using a centrifugal S/C kind of like the Procharger units. Have that feed into the intercooler, as well as the turbo, then have one larger pipe going to the throttle body. That way you're not pushing compressed air into a compressor and air can flow more freely. You'll have the S/C feeding down low and the bigger turbo, then the turbo taking over up top.
It's more expensive, but it's the way I personally would go if I were to do something like this
It's more expensive, but it's the way I personally would go if I were to do something like this