If you just use a pin in one leg, it allows you to more accurately position the figure in the scene if required. This allows the figure to pivot into position and you can make fine adjustments to things like facing, line of sight etc.
I usually use a pin in each leg to secure in my painting block, then when ready to mount the figure on its permanent base, remove one for the above reason.
Mike
"Imagination is the dye that colors our lives"
Marcus Aurellius
A good friend will come and bail you out of jail...but, a true friend will be sitting next to you saying, "Damn...that was fun!"