Space between magnaflex liner and prefab 8" chimney

I installed a Magnaflex Insulflex liner into my double wall 8" inner diameter prefab SS chimney this week. The Magnaflex liner has a stainless steel inner diameter of 6". Then it has an insulated wrapping and an outer aluminum jacket. The outer diameter of the aluminum jacketing is approximately 7-1/2". At the top, I used 3 screws to hold the liner to the 8" chimney. I reinstalled the original rain cap that goes on the outside of the double wall chimney.

My concern is that there is now a 1/4" gap between the outside of the liner and the inside of the 8" chimney pipe. Although there is a raincap covering this, my thought is that smoke particulate or other stuff could eventually collect into this area. Is this okay as-is or should I trim this out somehow?

I plan to have a block-off plate on the bottom but not sure what to do on the top. The raw edge of the insulation being "exposed" seems rather undesirable also. I thought of just siliconing a trim ring onto the OD of the 6"SS liner and letting it "hang" over the 8" edge of the Chimmney inner tube?

Thanks Brother Bart - That seems to be the best solution.

I attached some pictures (always better than the feable descriptions I am able to write)

Thanks to the others too for the various responses. My replies to those:

Cap supplied with kit: It really cannot be used if I install my original rain cap back on. It is more for use with a masonry application I believe.

Adapter Piece: The adapter from discount chimney may help solve the problembut for $70 I think I like Brother Bart's proposal.

The only thing that bugs me a bit is the exposed insulation. It does absorb moisture and although protected by the cap from bulk water, I could see blowing rain and snow getting in there. I might just pot cover the exposed edge with silicone to seal?

Thanks for your feedback!