Yes 2JZ twins are the same size, but the system works in a similar way.
Poodles said:
small turbo and large turbo doesn't work
small turbo ends up being a bottleneck and/or can't take the stress
at least in that configuration
I don't get what you're saying. Which configuration were you commenting on? The original post? He could open up only the small one at low rpm, then close it off, and open the larger one up at high rpm. How would that choke anything off?
As for AaronsSupraMKIII's post, that's actually a SERIAL turbo setup. If you have the smaller turbo operating at say a 2:1 PR (14.5psi), and turbo 2 operating at a 2:1 PR (14.5PSI) you'll get a net 4:1 PR (43.5PSI). Used for VERY high boost (think 100+ PSI). Not practical for gasoline engines because it'll detonate, but works very well on diesel.
The idea of the asymetrical sequential twin setup is actually a pretty smart one. I was seriously considering building such a setup on another car. The problem is it's very difficult to properly tune and control. You have to adjust a lot of things. You have two wastegates you can tune, you have a transition point you can tune, you have an overlap period you can tune. With that being said, tell him to do it. It will be bad-ass. Assuming he understands how it's all going to work as a complete system.