Hi there
I've been using HV20 with mounted shotgun and in manual audio mode. Problem is Im always worried about distortion. What are other peoples views on this? Do you use auto gain and live with the 'riding' sound levels?

I had the same problem, I tried manual and have got clipped sound, because it was too hard to change the level
;-(

I think if you are in a controlled environment you can do manual

If you shoot something where you cannot predict the sound level, you better use AGC