Installation problem: masonry chimney not plumb

[Freestanding]

I have a freestanding direct vent gas stove which vents to an existing masonry chimney using Dura-Vent Direct Vent Pro Masonry Chimney Conversion Kit ( specifically the middle piece pictured in the link aka the retrofit connector which hides behind the square piece pictured in the attached photo aka the thimble cover).

This retrofit connector should be sealed to my masonry chimney so that my intake air is pulled from the chimney rather than in my house. But it's not currently sealed. It's not even screwed to the chimney like it's supposed to be.

The problem I see is that the masonry chimney is not plumb. So if I screw the retrofit connector to the chimney, it will angle downward slighlty and won't perfectly meet the horizontal run of direct vent pipe. I suspect that's a problem.

What should I do?

And perhaps we'll save my leaning chimney for another post...

 

[DAKSY]

Is there a clay thimble in the wall behind the thimble cover?
If there is, you should be able to pack any air gaps between
it a the masonry adapter with un-faced fiberglass insulation
to block the air flow around it & allow for the combustion air
to be drawn into the adapter correctly...

 

[Freestanding]

A couple questions to help my understanding:

1) What exactly is the "thimble?" Behind the thimble cover is a round hole in the masony. That hole appears to be lined with sheet metal. Are you saying they are sometimes lined with clay?

2) Are you talking about regular old batts of house insulation? I would imagine I'd want something more specific to this application with more heat and flame resistance.

I appreciate all the info!

(The picture I attached doesn't help at all. But you can see my thumb on the thimble cover. Just to the right of that you can see the outer section of the retrofit connector that should be screwed and seal to the masonry. End the black part that's hard to see is the inner part of the retrofit connector which is the exhaust vent. )