Hi my current project is attaching a Watsonian Monza to my 1958 Huntmaster but sort just ground to a halt. Does anyone know the correct thread on the lower rear fitting point just behind the primary chaincase and below the swinging arm? My best estimate is 13/16 cycle (!!!?) 26tpi. I cannot find any mention on the net of specification so would be very grateful for any fellow Ariel owner´s experienced knowledge. Jim