Good.
Now, first thing to do is to make a backup copy of this version.
To a separate folder, or disk, or external harddisk...
Then, setup the stick, and buttons and whatever.
Copy conf.ini file and the folder named 'Users' to the backup copy of 4.11.1m
After completing that, make another copy of the 4.11.1m folder, the rename that copy to 1946HSFX (for instance) (on the same disk)
And install the HSFX mod in that one folder.
Not as backup, but as a running version.
Next, you can install 4.12.1m over the original 4.11.1m.
You now have two separate versions installed!
Create shortcuts to both the il2fb.exe files and name those in a way recognizable for you.
As you still have a copy of 4.11.1m as a backup, you can always revert back to that one if you need to start all over...
Good Luck!