There seems to be quite a bit of confusion regarding this topic. Everyone says that single wall needs 18". My stove plate and instructions clearly state that single wall can be as little as 12". My particular install is 16.5" to the pipe so its not like I cut it to the bone. Even so....what gives with the conflicting info? I have poured over past threads but didnt see anyone post the actual stove chart. Here is mine: Note the "A" measurement in the single wall section below.