Assuming you haven’t seen it already,(?) you might like this site:
I admit to being at a loss for “a CGS benchmark”. Was that a Coast Guard Station?
Those satellites you saw cross paths might have had 20 miles of height between them, who knows? But I agree it’s crowded up there. I’ve also seen a few cross paths. (I saw a couple of jet trails “converge” last fall. A strange feeling).
The mention of WWV and covering the lens for a moment reminded me of when I was reading about Apollo 13 a few years back, and found a site where I learned a few observatories, and amateurs, liked to follow the Apollo’s even headed towards the moon. On this link there’s mention of tracking a tumbling booster and covering the lens for timing purposes.
http://www.astr.ua.edu/keel/space/apollo.html
“CGS” = Coast & Geodetic Survey (Probably called something else by now). They were brass markers set into the ground. We found one in a country churchyard and did a few shots from there. The astronomers wanted a precise way of correlating the location of the photos in time and space. Actually I never got around to submitting mine, but I will never forget the first sight of Sputnik 2 sailing along, tumbling and slowly changing brightness just as predicted.