Convert stereo clip on stereo track to mono clip on mono track?

While recording voice overs, I mistakenly recorded them as stereo. I would like to work in mono only, because some audio effects generate undesirable stereo effect (e.g. the pitch shifter).

To go back to mono, I do this

(1) select all clips, right click, audio channel, and deselect the R box.

(2) create a new audio track that is specifically mono, and drag all the clips into this track

(3) add 9dB to all the audio clips, to compensate for the drop in volume. Don't know why.

If I skip step (1), the waveform display still shows stereo even after dragging into a mono track. Strange.

If I skip (2), the sound comes out only from the left speaker.

Is this the best method? Is there a way to convert the audio track to mono, instead of creating a new mono track and then drag all the clips onto it?