Insert direct connect questions

First time poster here. I am looking into getting an insert (possible Avalon Pendleton -- so far it's the only model I've found that will fit my tiny 13" deep 24" wide fireplace) and am just starting to learn about the flue connection options and issues.

I have an existing insulated steel chimney liner that was installed about ten years ago (cost $1600), but it only runs to the top of the smoke chamber. I have received contradictory advice from the two places where I'm shopping for inserts. One says I should get a good draft with a direct connection since the majority of the chimney is lined. The other wants me to remove the existing lining and replace it with a longer one to reach the stove. (I asked about possibly extending the existing liner but he said it has to be fabricated in one continuous piece and can't just be joined together like heating duct. Can anyone confirm whether this is really true?).

I also asked about the cleaning issues with a direct connection, and he said that the stove needs to be moved out no matter what, because chimney cleaners in our area (Boston) no longer go up on the roof to clean from above like they used to, but only clean from below now.

Anyway, given the very high cost of replacing the liner, my thought was to just go with the direct connection and see how well it works, rather than pay a lot of money up front to replace the liner to solve a problem that may or may not exist. Does that seem like a reasonable approach?

Thanks for any advice,

Jon

The existing liner is rectangular -- I can see the end of it looking up from the fireplace but cant easily get a tape measure up to check the exact measurements. Maybe 7 x 5 inches? But the damper opening is only about 4 inches wide, so I think there is no obvious way to reach up from below to attach a coupler and and a new length of liner. So if it were possible to extend it I suppose it would have to be done by either (a) attaching a coupler and an extension section from the top and then sliding the liner down the chimney through the flue and then using a rectangular-to-round adapter to connect to the stove, or (b) pulling the whole thing out, attaching a rectangular-to-round adapter and a section of round liner to the bottom end and then putting it back down the chimney.

Update: advised by Avalon stove dealer that direct connection is preferable because positive connections tend to overdraft. However, I then met with a chimney pro who (after looking at my chimney in person) recommends pulling out the existing liner, attaching an adapter and extension section at the bottom, and then feeding it back down. He says the stove dealer is nuts and direct connections are a bad idea on many fronts. Since he deals day in and out with chimneys and stoves that are already installed, not just the day they go out the door, I'm giving him more credibility and go with his recommendation and will have him do the flue work and install the stove. I have to do some tile work first but expect to have the stove installed within a few weeks.

Just thought I'd come back and post the conclusion of the story in case anyone with a similar situation finds this thread. What the chimney guys did was (1) pull up the liner from the top just enough to attach another short section of the same dimension rectangular liner, then (2) drop the liner with the extension down the chimney into the firebox (after knocking out a lot of brick that was in the way) where they attached (1) an adapter from rectangular to 6" round, and (2) an adjustable elbow to compensate for the fact that the chimney was about 3" off center relative to the fireplace. I only got to use it a couple of times last spring; the draft is definitely very strong, so I hope it doesn't get too much stronger in colder weather.

Re:cleaning. They said they will clean from the top down, though it will be more expensive because they have to set up scaffolding on the roof (see photo). re: silicone. damn, these guys are supposed to be pros, that sounds like a rookie mistake. I assume at this point the only thing to do is let it eventually burn off (assuming it does actually get hot enough)? Is it worth trying to scrape it all off with a knife? If it does burn off, do I need to re-seal with something else or can I just leave it unsealed?