When you need a really robust support fixture to hold a component in an exact position the Fisso 5000-62 articulated stand is the answer.  The stand is shown here fitted with a 75mm pipe clamp next to an 18" length bar to give a size comparison. 

Many applications  include holding auto panels in position during manufacturing quality control. The adhesive power of the magnet is 1200N with a radius of movement approc 600mm.