A support frame rail with a central longitudinal axis is orthogonally coupled with a pivot beam. A support frame plate slidably couplable with the support frame rail includes an embedment projection. A hanger plate is fixable couplable with the support frame rail. A planar support platform is pivotably coupleable with the pivot beam. A saddle has a pommel portion, a saddle support portion, and a connecting straddle portion. A saddle bearing assembly defines a first rotation axis and is rotatably coupled with the saddle. A support frame bearing assembly defines a second rotation axis collinear with the central longitudinal axis. A pivot arm assembly is rigidly coupled with the saddle bearing assembly and the support frame bearing assembly. The straddle portion has a triangular cross-section, and enables adoption of an unsupported standing position, a partially supported standing position, or a weight-forward standing position, by a hunter straddling the straddle portion.
