I have a full Yakima set up on my shell including, tracks, footpack, and crossbars.
I started with that same setup but ditched it after a few trips. The weight of the tent combined with the height of the crossbars created a lot of torque and caused too much side to side movement on the trail.
I drilled holes through the tracks and mounted a set of Thule bars directly to the shell.
I leave the Yakima feet on the tracks and can still use all of my Yakima accessories:
I have two Thule bars connected to the RTT that mount directly on top of the Thule bars on the shell (total of 4 Thule bars):
I drilled holes through both sets of bars and connect them with an extra set of RTT clamps using grade 8 bolts (1 clamp on each bar end= 4 clamps total):
Lowering the RTT just a few inches made all the difference: the weight of the tent is barely noticeable on the trail, now. It also fits in the garage without having to air down the tires. We only install the RTT for camping trips and have used this setup for >15,000 miles and many, many nights. A good number of the miles have been offroad and we haven't found a single sign of fatigue or experienced any leaks in the shell (just got back from another wet trip to the PNW).