Whilst eating my breakfast was watching this clip of an ingenious method of turning a concave or radius,quite uniuqe,as I watched it a second time it suddenly dawned on me...Why make a platform for this turning action? all we have to do is remove the position pin from below the toolpost put a smooth washer on the toolposts spindle,put toolpost back in place but leaving the locking lever loose,fit a square piece of rod in the right hand side and sticking out towards yourself,put a toolin the lefthand side of the toolpost as per normal and the same action can be replicated in the vid.

Simple no?