First off, what I'm going to say applies to Slackware, so I have no idea if this applies to Salix too.
I'm pretty sure activating the SUID bit in /bin/ntfs-3g is not needed and you don't need to belong to the disk group. I have an external hard drive with a NTFS filesystem and I can use it normally. HAL mounts it and I'm able to write to it. I don't recall doing anything special to be able to handle this. Have you tried giving everyone "total control" to every file in the filesystem from a Windows machine?
users lp uucp audio video cdrom plugdev power netdev
$ ls -l /bin/ntfs-3g
-rwxr-xr-x 1 root root 50392 Nov 6 22:09 /bin/ntfs-3g