Mike, I didn't read the other thread but this is a good place for your question.

My system is a lot like yours. The exception would be that I have two internal drives dedicated to BIAB. The program is on its own small SSD and the RealTracks/RealDrums are on their own fast Western Digital Caviar drive. Keep in mind I have the audiophile edition, so it's 11 times larger than the 'regular' version.

In your case, unless and until you might go the route I did, I would install the program (only) over top of your existing C drive. Most of the files are already there so the space will not markedly increase. In the install process as I'm sure you already know, you can direct the RealTracks & RealDrums to a different drive. Again, most of that content is alread there. BIAB only writes the new material and any updated files (and there are some this year).

While USB drives are certainly up to the task of running BIAB and you can even run the whole program from one, any internal drive (even a hard drive) will still outperform the external drive. It may be a luxury to have my program on a separate SSD drive, but I use BIAB every day for work and I do enjoy the extra pep I get.

Jeff gives a good tip about free space. Some experts recommend 15% on hard drives and even more on an SSD. And make sure the Trim function is on for your SSD (or run it manually every month), and never Defrag one.

BIAB 2025 Win Audiophile. Software: Studio One 7 Pro, Swam horns, Acoustica-7, Notion 6, Song Master Pro, Win 11 Home. Hardware: Intel i9, 32 Gb; Roland Integra-7, Presonus 192 & Faderport 8, Royer 121, Adam Sub8 & Neumann 120 monitors.