Apart from that mod, I don't know of a way. Obvious question - are you sure you're installing it right, because it was a notable difference for me. Unless the mod became standard in an update or something.
Additionally you can edit your PLR file - there are some options in there about what appears in your mirrors or when you look back. That might help clear it up for you.
Not sure about the mod, I'd have to re-download it and check.
In the PLR file there are many options, so just scroll through and take a look. There's something like "Self in cockpit rear view" and similar. Another about virtual mirrors in cockpit. Try those, and like I said take a look at the rest.
There are 2 text strings about it: Virtual Rearview In Cockpit "0" / "1" This enable the three virtual mirrors on the top as in swingman view Rearview="1" // 0=Off, 1=Center and Side, 2=Center only, 3=Side only (virtual mirrors only, in-car mirrors are on/off) and this one reproduce the three variants of the real onboard mirrors
You can use it both togheter as in a room of mirrors...