The Hullavator needs to be mounted on Thule cross bars, and the bars need to extend toward the outside of the car a certain distance so that the arm doesn't hit the side of the car in the down position. It cannot be installed on the Premium's plastic rack, unless you can somehow attach Thule bars. I bought the Touring to get the Thule bars for a Hullavator for my sea kayak.
Thule's solution to the outback plastic rack is to clamp their crossbars to the subaru crossbars in the stowed position, which means extra height and a maximum crossbar spread of 24.5." You can alternatively go with the Yakima Skylines that mount in the holes in the plastic rack and use their Showdown load-assist, so 30" crossbar spacing, but still higher off the roof than ideal.
And in other news, Yakima has finally introduced their landing pads for the touring rails, so that provides another option if you have the touring rails.
Has anyone successfully mounted Thule Hullavator to Yakima Jetstream bars (connected to roof via Skyline towers and Landing Pad 15)? And if so, what bar length did you use? we are considering getting a 2019 premium... and would love to use the Hullivator like we did on our Forrester. On that vehicle we have Thule 53 inch bars, but Yakima come in 50 or 60 inch lengths... so am not sure which one we would need