When installing a TK application, mount the bases first before you try and configure the actual Tracker foot. Use reference points on the roof to determine equal measurement on both sides of the car, such as a seam in the track, a bolt hole, or the actual end of the track.
Utilizing the T-Slot with Thule Xadapt Kits in the AeroBlade allows you to use the entire bar length for mounting accessories, since the tower is inserted below the bar.
Use this guide to determine if you are able to use longer AeroBlades than the specified size for your vehicle:

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