I am connecting an VC Encore to double wall Selkirk 6" pipe (DSP6 also sold as Metalbest). I live remote so ordering online. The stove store says I may need a special connection from the stove or it will whistle. Selkirk has two stove connectors. One is just called Stove Adapt0r (DSP6SA-1) and the other is a Flush Stove Adaptor (DSP6FSA-1). The store says some people use a single wall at the stove then adapt to the double wall to prevent whistling. Hoping to get the right adapter on the first try, although in many plumbing and venting projects that is difficult. I need to stick with Selkirk DSP double wall as my Class A already installed from before is Selkirk Metalbestos.