Same thing happened to me, what I did was buy a single wall double male piece. The single wall double male is a true 6", I first inserted it into the stove's collar then ran my hand into it to feel how much I would need to trim off so the single adapter doesnt sit below the collar on the inside of the stove. I think I took off just over 1/2" off the end of the pipe, then screwed it to the stove collar
I then took the dvl adapter which has the inside crimp connection at 5 5/8" wide and slid that into the end of the double male, very snug fit, popped 3 short screws in that, then attached the dvl pipe to the dvl adapter. Works like a charm and very happy, I originally just had the dvl adapter sitting on the flue pipe and had issues with air leaks (whistle sound) now I'm running nice and quiet, plus I like using the damper on the dvl, 3/4 closed is my sweet spot when its windy out.
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