Hi Graham,
When you say that WebDav Performance in Windows 7 is poor what WebDAV client are you using which is resulting in this poor performance? In LabVIEW 2013, their is a WebDAV Client API of which I've referenced a simple put/get example below and from my testing I observed transfer rates ranging from ~ 18-23 MB/sec on our internal GigE network.
If you do not wish to develop your own WebDAV client in LabVIEW for these purposes, another solid WebDAV client is Cadaver. To run Cadaver on Windows you will need Cygwin. During the Cygwin installion you will need to add cadaver from the web related selections to add that support.
If your observed poor WebDAV client performance is specific to a Windows client (say IE), then there is little NI will be able to do to improve the situation other than to suggest alternative WebDAV clients, or for NI to suggest workarounds such as the one you pointed out earlier.
If you have any further questions please let me know. Have a nice weekend!
Blayne