You have to be brave and edit Generic 0 first. It's so full of pointless duplicates it's a crying shame. Doing that affects all others for starters. Plus you only need 3 types of flat roof per set which lets you have 3 types of pitched roof per set; makes any town map look more varied. A super big set with all just isn't easily acheivable imho. The original guys even had to pull back from what they were doing (each set was meant to have twice as many tree types available but it didn't work because it went over the paragraph limit per sub section).