I tried the scanner group and all, but come to think of it I am using an older TC version at the moment (which is normally fine to upload extensions with, but the udev stuff could already be fixed) and I will sort this out tonight. If sane as user is supported by udev/group then xsane would by definition be also.
Oh, would you mind if I made a xsane-standalone extension as xsane pulls in cups, hplip, perl, python, and a lot of other stuff. Don't get me wrong, it is great we have all that supported, but an option for a simple gtk1 xsane that would require only sane-backends and libusb would be good to have too.