vambrace (armour for the upper arm)

Upper cannon of a right vambrace (rerebrace) of moulded leather. Originally tubular, it has been flattened into its current rounded T-shape. It has a pair of holes at the top for points, a slot with the remains of a leather strap at the centre of the outside edge, and slots for two more at the centre of the inside edge, one containing a strap fragment, where it was originally strapped round the arm. Inside is a separate leather lining, of softer leather, with a repaired cut. The exterior is tooled, stamped, incised and modelled with diaper design of foliage inhabited by birds and mythical two-legged beasts, and a plain border. The upper rear border has been cut off.

I just finished making my splint vambraces, but I wanted to know just how imperative a vambrace on your shield arm is? I'm aware that it's not technically required (at least in