Pellet to Wood Stove - Remove Adapter from Ceiling Box

[Sparky0427]

I am replacing a wood stove with a pellet stove. The vendor I bought the pellet stove also supplied me with the exhaust pipe and adapter 4pvp-x6 to utilize the existing 6" I have removed the old stove but when I go to install the adapter, there is some wiggle room on the ceiling adapter. I reached to DuraVent who stated "Outer wall fit does not matter but the fit on inner 6” liner to 6 inch adapter sounds like there is a ¼ inch gap 😉 you could center and screw then seal gap with a ½ inch bead of the 500 silicone sealant. If you can trim off or pull out the single wall adapter our part will fit up into (at least a 6 inch) hole and then we screw the round trim ring to the bottom of the box. Either will do" My issue is, I can't get the single wall adapter out.

Any suggestions? I was leaning towards installing the DVL adapter 6DVL-ADT as they suggested.
Below is a picture of the adapter that is installed.

 

[Sparky0427]

Determined that the box is made by Security Chimneys and has a Integrated adapter so I ended up centering the DuraVent 4PVL-X6, installing 1" screws and then sealed the gap with high temp silicone sealant.

Hope this helps others.