Hi Mark, its great to hear from you!!
I think that absolutely, in my opinion, these shellguard espadas would have been perfect for piracy in the "Spanish Main" which carried on in the Caribbean and Spanish trade routes well into the 19th century. As we know, heavy British blades are seen on some, while the lighter and more decorated blades may heve been used by the gentry in South America. I had always heard of 'espada anchas' (generally applied) in South America, but until the Brazilian ID, had not seen examples.
There is apparantly a new book out on sea service weapons, cannot think of the title offhand, but its author is named Sim Comfort. It seems highly regarded but is also mucho expensive! I'm hoping to discover more on it, and maybe such examples might show up here.
I'm with you on the maritime plausibility for these shellguards, just as we discussed before

pirates at heart we are !!!