For our tracks, and most other "C" channel tracks including Thule, A.R.E , and others with the "A"channel measurement of approximately 3mm x 20MM. see image below, you will use Landing Pad 1 along with the SkyLine Tower.
You may also be interested in this article, What are the dimensions of your tracks? which provides more information on the tracks themselves.
Example of a "C" Channel Track
Landing Pad 1
Crossbars: To determine the proper bar length measure from the center to center of the tracks and add 2"