Samba is working perfectly for me, thanks for the pointer.
We are using TinyCore in virtual machines, hosted with VirtualBox, to stage simulations of our server-based software. We want to fire 5 or 10 of these simultaneously on a laptop, so memory footprint is a huge issue for us. I wasted a day or two trying to get the VBox "guest additions" library working as a way to share our windows files, but it requiring persisting so much stuff that I concluded this should only be done by formally building a TCE or TCZ to deploy it.
Now, with Samba we have writable and readonly access to windows shared files, so we can provision libraries and scan log files on the windows side and be in sync with the background unix servers. In fact, it'll make it easy to run headless, possibly letting us squeeze the footprint even smaller.
Thanks to those on the forum who provided the valuable info that allowed us to get this far.
Cheers,
Dave