It would be nice if the installer allowed users to install to a different location.
Upon running the Win64 bit installer I get a message that states OpenToonz is already installed and that the current installation must be uninstalled before proceeding.
Added: I *think* a workaround is to uninstall the 'official' install first... then install the OT with MyPaint (installing it to different location and with a different stuff directory is likely ideal.... then reinstall the official release and allow it to install its defaults.
The thought being that other installations likely should not compete for the same space on a harddrive as the official branch of OpenToonz.
Hope all of this makes sense!
I'm investigating your OT with My Paint now! :)