I do Split Stereo Track, delete the duplicate and set the remaining one to Mono, will doing it that way work, Blastdown?
Yes.
The difference between the two is that
Stereo Track to Mono combines both sides of the song into one, while
Split Stereo Track only gives you one side of the song.
This might change how your song sounds if, for example, they have a special sound coming out of only the right side and you deleted that part. In the export you would not hear it.
I would suggest using
Stereo Track to Mono unless you have good reason not to.