I think you would more want 20 gauge, especially if they are large - the weight wears on your shoulders after a while. If the pauldrons are well-shaped, they will be an arch in cross section, there will be some overlap of the lames of the pauldron (which should articulate well, or they will become quickly unbearable, and impossible to fight in), and in addition, using stainless steel, this should make them reasoonably strong.

Consider, you would be wearing a cuirasse, which will add weight to the shoulders, and in addition, with pauldrons you would be wearing full cannons of the vambrace - a very cople, hard articulated arm defense - too much weight will drag you down, and slow your ability to defend yourself, to engage in any skilled activity such as riding, etc.

Historical armour is much thinner than the vast majority of modern reconstructions of it. A full harness should weigh between 40-50 lbs, and many modern ones have people staggering around in 80 lbs of harness, or more, of much too-thick armour.

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