I mount our RTT directly to the stock rails on my 4th gen (with stock crossbars removed). To have the tent open to the side, you need to rotate the tent rails 90-degrees and shorten them a few inches before bolting them to the tent base so that they essentially become your crossbars (very easy to do). It is about the lowest you can mount a RTT, and saves a ton of $$$ on an aftermarket rack.
FWIW, the Smittybuilt RTT looks pretty nice for the money. From the pictures, it looks amazingly similar to all of the other RTTs that are sourced from China (CVT, Tepui, etc.), and probably even comes out of the same factory.