| Is there any way to install without uninstalling the bad one; that
| is, without uninstalling v11 completely)?
Yes. While approved methods may exist, you can also use my method, which is
totally unapproved by JPsoft. Use 7z to expand the installer into an empty
directory, and use move/u to update installation directory. Alternately, you
can use 7z to just update the installation directory. Of course, TCMD and
TCC V11 must not run at the time. I do it using V10.
Warning! My method may not work for future builds!