For anyone looking at this, between the help I've gotten on this answer from @ReinderWit as well as the answer from another question (see the other comments in the question) I was able to figure out how to build up the XDocument.
The code follows:
_folderviewContents =
new XDocument(
new XElement("InterfaceIdentifier", "835"),
//Start of FolderPaths
new XElement("FolderPaths",
new XElement("Folder",
new XAttribute("fromDate", String.Empty),
//attributes for Folder w/ lots of attributes
new XAttribute("toDate", String.Empty),
new XAttribute("contactName", "APerson"),
new XAttribute("email", "AnEmail"),
//value for that long Folder w/ lots of attributes
"Remittance Advice"),
//Facility
new XElement("Folder", String.Empty),
//PayorID
new XElement("Folder", String.Empty),
//RemitDate Year
new XElement("Folder", String.Empty),
//RemitDate Month/Year
new XElement("Folder", String.Empty)),
new XElement("DocumentType", "RA"),
new XElement("DocumentDescription",String.Empty),
new XElement("TotalFiles", "1"));
I still need to add the XML version and the Namespace, but those seem simple enough to do. Hopefully this helps others in the future with building XDocs that are a bit weird and not-so-straightforward.