Let me know if I’m wrong, but I think that if you just use the “fill right” effect, it will take the right channel and fill the left channel with it. It sounds to me as if you’re taking the empty channel and trying to put it somewhere. The naming of the effect is a bit counterintuitive, but if you read the help file, it seems pretty straightforward. Here’s what Adobe has to say about Preference settings (which you can change, by the way):
Default Track Format Defines the type of track in which the clip audio channels are presented when a clip is added to a sequence—Mono, Stereo, Mono As Stereo, or 5.1.
Mono Maps the source audio channels so that they’re placed on separate mono audio tracks. For example, when you select Mono from the Default Track Format menu, Premiere Pro maps each source channel to a separate mono track on capture or import. If you capture from a stereo source with this setting, Premiere Pro maps each of the source channels to a separate monaural track. You can apply the Mono track format to clips containing any number of audio channels. Importing a file containing 5.1 channels maps them to six audio tracks. When you add the clip to the sequence, the clips on the separate mono tracks remain linked together.
Stereo Maps the source audio channels so that paired channels are placed on stereo audio tracks. You can apply the Stereo track format to clips containing any number of audio channels. If the clip doesn’t contain an even number of channels, a silent channel is created. The silent channel is paired with the unpaired channel when the clip is added to a sequence.
Mono As Stereo Maps the source audio channels so each is placed on a stereo audio track. Premiere Pro duplicates the audio from each mono source channel and places it in the left and right channels of a stereo track. You can apply the Mono As Stereo format to clips containing any number of audio channels.
5.1 Maps the source audio channels so that one or more groups of six channels are placed into separate 5.1 surround audio tracks. If the number of source channels is not a multiple of six, Premiere Pro creates a 5.1 surround audio track with silence on one or more channels.
Joe Bourke
Owner/Creative Director
Bourke Media
http://www.bourkemedia.com