When I initially got this lit up, with too much happening, I saw smoke leak at the top, not the bottom even though the middle section does require a slight "placement" down into the bowl. Overall I think it fits together well but that the lid isn't designed to seal as well as the middle section-to-bowl.
I'm interested in sealing the top and door for sure but since I'd be getting a kit or roll, would presumably have enough to include the bottom too.
And I know I lit too many to start, a full (smaller) chimney.
The 18.5" I bought my brother-in-law last year hasn't been used yet, partly because he doesn't know how/hasn't been interested to explore and partly because I'm not often in town long enough to assist. BUT, I remember his middle section fits his bowl poorly and I wasn't able to bend it back very well. I'd want to work on his sealing better before him having an initial bad experience. Maybe there's a thicker/uglier gasket for that situation.