That's an interesting guess and certainly seems to match the general body profile well. However, the color patterns on both the tergites and sternites are very different from those in the Spinadis simplex
specimen you uploaded to bugguide.net earlier this year:
Another page on there led to this paper describing the first adult of Spinadis simplex
This characteristic seems especially relevant in the description of S. simplex
, and doesn't seem to match this specimen: "The fore tibia is approximately three times as long as the tarsus, and one-third the length of the femur."
Another important one is, "The hind tibia is 1.16 times the femur length." They note this is also present to some extent in the nymphs.
Also, the shape of the subanal plate is pretty different and is noted as a valuable characteristic.
The paper also extensively describes the characteristics of an enlarged pronotum in S. simplex
that doesn't seem to be present in this one.
Finally, the habitat is very different; this came from a smalls stream distant from any of the large rivers previously described as Spinadis
I still think this is a dun -- the wings are quite pale for a dun but not really hyaline like a spinner. My early photography didn't make this particularly easy to tell, but you can also make out setae on the margins of the wings in this picture
The dun-spinner difference might explain some other differences including the leg proportions, but I think enough characteristics differ that it's probably not S. simplex