After a brief encounter with a very basic bar rest as a child, my teacher recommended a Wolf and it's been my shoulder rest for both violin and viola for about 30 years now and the one I recommend most frequently to my students.
They didn't yet offer the Forte Secondo model when I was first starting out, so I used a Primo initially. In my experience, the Primo has the same flexibility as the Forte Secondo, but better for bigger, broader shoulders and chests. Paired with a well fitting chin rest, the half moon shape of the Forte Secondo helps the instrument hug towards our center of gravity, keeping the left shoulder mobile and the instrument secure. Height and tilt can easily be adjusted, but not everyone may know that the bar can also be bent and twisted to hook over the collarbone and contour to the upper chest for a highly personalized fit. This feature is a complete game changer. To get a similarly personalized fit in a rest we would probably have to look to Pirastro's Korfker, but they cost hundreds of dollars! Right out of the box the bar of this rest is usually completely flat across and that is usually uncomfortable and often too high for many people, event with the feet wound all the way down. It sometimes takes a few days or weeks of experimentation, but it becomes a completely different rest once we've bent it to suit us, so stick with it!
A number of years back a new violin student showed up with a box full of shoulder and chin rests that she had tried over the years (and disliked). She hoped I might be able to find new homes for them but most remained orphans, maybe because there was not a Wolf in the bunch. However, through that I was able to spend time with about 25 different shoulder rests. None were as comfortable or had the seemingly endless flexibility of the Wolf Forte Secondo, making it the winner even over popular Kun, Match One, and Bon Musica styles.
The only concern I feel with this rest is that sometimes once we've bent it into a contour we like, the metal arm that allows us to extend or contract one of the feet may stick up and potentially scratch the instrument. In those cases I've had students cover the tip of the metal with duct tape. A more permanent solution could be to get a tool that can cut through fairly sturdy metal and and cut that arm a bit shorter.
Available widely online and in shops, you can also view the Wolf line of rests here https://wolfproducts.com/products/shoulder-rests.html
