The composite image (above) compares Mill Valley AFS when it had two AN/FPS-6 height-finder radars and the AN/FPS-26 height-finder radar under construction (top) with the later shot taken from roughly the same place and angle (bottom). Both views are from the cantonment area looking east.

Notice the AN/FPS-6B / AN/FPS-90 radar tower on the left in both images. Either that tower got shorter, or it was moved further away. I am pretty sure it was the latter. I always thought the location of the AN/FPS-90 tower seemed odd, being right at the point where the access road meets the top site. I suspected early on that that tower maybe was moved there when the AN/FPS-26 was installed (to get greater separation between them). And I think these two photos offer proof of that.