Has anyone ever put a 7 speed cassette on a 6 speed uniglide hub? I have the cassette but the top cog seems not to want to thread on 100%. Right now, with the hub not laced, it looks more like 60%.

Is this normal? It is hand tight. Will I squeeze more slack out of the cassette when I pedal on the top cog? Will I damage the threads? My hub is a dura ace six speed gauging from the wear marks.