If you've ever noticed a "soft" less than solid feel when tightening the rear seat bolts on your XT there's a reason for it, the nuts imbedded in the seatbase are barely holding on, in fact recently when I dumped the bike my boot cuff snagged under the side of the seat and pulled the seat right off ! with the bolts/nuts still attached to the bikes frame.
Link to seat mod
http://bultaco.proboards.com/index.cgi?board=yamahaxttt600
Link to seat mod
http://bultaco.proboards.com/index.cgi?board=yamahaxttt600