Does your audio program provide a stereo > mono conversion?
If so, zero out the 'backwards' (which btw should be the right) channel and convert the rest to be a mono sound file - the original two track recording is mono anyway.

And further, if your fourtracker has a switch to mute the 'backwards' ch, you could do the recording onto the pc in mono mode in the first place, provided your software gives that choice. Or you could simply connect the 'correct' track only.

I'd prefer keeping a mono recording as it is, because duplicating it to "stereo" (two similar tracks) does not enhance the sound at all, on the contrary in many cases.

AKS