It seems like an easier step would be to partition Windows during the installation process. There used to be a way to do this. Is partitioning a Windows drive no longer possible during the installation process?
I made a dual install for my laptop a while back on a laptop that came with Windows 7 already installed. I had upgraded to Windows 10, and since it was the home edition, I had no control over when it updated. I used to take the laptop out and sometimes use it on public WiFi, but it would update without my consent. I then decided to install openSuSE on it. I used a third party partition manager to repartition the Windows Drive, then installed openSuSE which uses Grub as the boot loader. Grub still saw Windows 7 as an active OS, so I had to tell Grub to ignore it. But once I did that, the boot loader still had openSuSE and Windows 10 as boot options.
If I could get openSuSE to hibernate properly on closing the laptop cover, I would just drop Windows altogether; however, for some reason, the hibernate on closing the cover feature for openSuSE does not work properly - it sleeps the PC instead.
Now, whenever I want to use public WiFi, I use openSuSE and rarely connect Windows to the internet even though I upgraded it to the Pro version.