I went out at 1pm and uncovered the panel and did some tests. Unfortunately, it's overcast, so I was only getting about 50% power from the panels
(about 2.5-3 amps)
I experimented with shading the panel. This is in overcast conditions, but I held large rectangle shade over panel. If I put the shade flat over top the panel and shaded even down to 20% of the panel, it would still pretty drop to nothing (less than 1 amp). Which end didn't matter. Which side didn't matter.
If I held the shade on end, so the shadow was only 1" wide or so, I'd lose 50% power, so it would drop to 1.5 amps or so.
Not a very scientific test, I admit, but at least I know now that if a line crosses it, it might still put out some power, but if a spar shades it, no bueno.