I doubt that the Subie crossbars will fit the 4Runner rack unless they are an aftermarket universal fit style, then you might get lucky. Thule, Yakima and Rhino Rack (plus a bunch of others) make crossbar systems that rest on top of your factory rails and use a band or clamp that attaches them to the rail. As far as roof top carriers go, it depends on what you are carrying. I have an old Yakima that I could literally sleep in (180 cm x 90 cm) that is still great after 20 years. I also have a Thule that is long and skinny for skis (210 cm x 60 cm). The problem with them is storing them when not in use. They are heavy and cumbersome. If you can get away with a soft carrier that can be used as is on resting in a roof basket, that is a great solution- light, easy to store. Both e-trailer and rackoutfitters.com have lots of videos on different racks.