I think the balance of probability (and the rareness of types like the 504 in the USA) leans towards the likelihood of these being Palen's.
Fair enough.
Just noticed on that site another image has been uploaded, most likely from the same day, this time a Bleriot!...
Just seems strange to me that more isn't known about this event. It would have been a BIG day for Palen, no?
Cheers!