Why do you need SISR for this? If he game is receiving input from the real stream controller (as you wrote), why not just disable SISR and go along with that?

Anyway, what you can try is to disable one of the controllers in the “Game Controllers” section of control, as outlined here: github.com/…/Methods-for-Disabling-Joystick-Readi…

That website also include some more advanced methods, but I don’t think they will apply to your usecase, unless you want to run SISR as a different user.