I will offer my opinion On the "SOS".
It is too short for mounting on the lower right. It is not designed to mount on the upper right. The deployment is easy enough and getting it to fill is easily accomplished.
Much of the tube is used up following your torso with only a couple of feet extending above your head. This leaves a bit to be desired in 4 foot swells. You may need to add air using the power inflater to get it to fill completely. Your BC will be fully inflated when it is done.
Once at the boat, storing it conventionally is out. The easiest way is to slightly deflate, bend it forward, and tuck it into your cumber bun or shoulder strap. Once on board you can remove the BC, and roll it back up, and store it for deployment.
It was a neat thought. In it's current configuration it is not worth the purchase.