Low G in R-22
Low G can/will indeed happen when hitting a strong downdraft.
This low-G should be treated with the same remedy as a pilot induced low-G : take the cyclic aft gently to reload the disk.
Some time ago this was discussed, some pilots had some ideas about using pedals (not me), but a plank like left pedal is most certainly not the answer, it is dangerous.
Downdrafts in moutainous areas just don't fall out of the sky, they are quite predictable, when one observes the mountain ridges vv the wind. Many times they are preceded by an updraft. In that case flairing in advance at the first signs while reducing speed is what I would advise (during the previous updraft), because in the downdraft you can pull some extra collective.
d3