This has been discussed many times. The properties of the discussed systems should already be clear. Now is the time to decide what is the easiest system to serve, and which gives the best start-up properties at the next start-up.
Condensing in a single cylinder with a loose inner sleeve and a loose gutter is the easiest to serve in the long run.
The gutter formed as a “piston ring”, pressed to expand by a horizontal bolt from one gable to the opposite gable.
Gable = short (end) wall on a rectangular house.
Then you want to exploit the heat in the exiting gas:
With a plank, internally and externally cleanable from above without dismantling anything.
No exit heat will be lost to the crows before delivered in the midst of the wood.
Why always chose less effective ways, when more effective ways are more practical
to use and serve?