» Tue Jun 19, 2012 12:18 am
First, make your new set of armor. Create and add an identical keyword to all 4 pieces of said armor. For example, "Brotherhoodunenchant".
Then, edit the Light or Heavy Matching Set perk (Abilities > Perks > Matching Set), right click on the Modify Armor Rating entry in the table at the bottom, and duplicate one of the conditions (or do "New" and just mimic the existing conditions). Change the keyword in the condition to the keyword you named your new armor pieces.
That basically tells the perk to check your character and see if they have at least 4 pieces of equipment marked with the keyword you specified (4 pieces = full set) and if you do, multiply the armor rating by 20%.
Alternatively, you could mark your new armor with the same keyword as the vanilla Dark Brotherhood armor (which is "ArmorDarkBrotherhood") so that your unenchanted armor could be mixed and matched with the vanilla enchanted armor and still give you the bonus. So say you wanted to wear your unenchanted body, cowl, and boots but still wanted to use the 2x backstab from the default Shrouded Gloves, you could do that and still get the matching set bonus.