|Yeah, good luck on the beach.|
Shields as DR: Shields can be used with DR, just like any other piece of armor or cover. QAGS already gives us a guide for armor and cover which in this case would stack with shields. I can see this working in a number of ways.
-For an older school flavor, Shields add only +1 DR. It's kept nice and generic.
To add a little more complexity, just a pinch, Shields can be placed into two categories: Light and Heavy. Light Shields add +1 DR and Heavy Shields add +2 DR
Shields as a Penalty: Now armor, the kind you wear, is armor because it typically covers a lot of your body that it is often struck in the course of trying to attack the character (which is why DR is applied). Shields are used as part of fighting to help deflect attacks from the target as opposed to being stack stuff you wear to absorb blows. Using these rules the shield modifiers the opponents attack.
A light shield: -1 to attack.
A heavy shield: -2 to attack.
Depending on how large of shield are we talking about (from light to heavy to all the way to ludicrous size) it increases the penalty to attack with each step you wish to add.
Old School Style Shields: DR +1
Slightly More Complex Shielding:
Light = DR +1
Heavy = DR +2
Shields a Penalty
Light = -1 to Opponents Attack
Heavy = -2 to Opponents Attack