I have about a thousand hours left PIC AS350 B2 & B3. I have flown not a huge amount of sling jobs. Although I have done Human External LL, drill support/moving, bucket work, and of course cargo hauling. I really enjoy flying from the left. I learned to long line in one from the left, so it is all I know. Did 20 min from the right through the vertical window once, was ok, but not nearly as good as from the left. This being said that there are masters from either side, although I would think you will learn faster and be more proficient with less practice from the left. The key is that you have an arm rest. Also a bubble window is a nice benefit when it is cold or rainy. Plus you can lean against the door. The STC in US for this is owned by TEMSCO in Alaska I believe. I imagine you can contact them about where to buy one. Talking with ground crews over the years they all say that working with helicopters where the pilot is on the left, they are almost always faster. There is much better view of what you are doing below you. Also much better peripheral vision, this of course is used to fly a stable hover. I will say that it is not necessarily the most comfortable for the pilot, so if you have to be "out" all day that can do a number on the body, mainly neck and back. So not all peaches and sunshine. Also often needed to remove the shoulder harness to lean out far enough, so lose a bit of safety. I will see if I can find some photo of the setup. AGO