I built this mount for use with my ST80, but since I sold my ST80 (and ST90), I no longer need this mount. The tripod is made of oak and the mount is made of baltic birch plywood. The ST80 mounts to the cradle with a 1/4"-20 bolt (supplied). Height from the ground to the bottom of the rocker box is only 36" which makes it a nice sitdown setup. All the hardware is stainless steel except for the pivot bolt on the rocker box and the three galvanized steel carriage bolts at the end of the legs. Finish is a couple coats of polyurethane. And yes, those are rubber bands that I used to adjust tension - it worked <g>.
$90 (includes shipping)
Money orders only,
p.s. An ST90 will work with this mount, but you won't be able to quite reach zenith with it because the diagonal will hit the rocker box. (been there, done that)