Re wall exit and muffler
@Listernational.....our listeroid is in an open shed, the exhaust exits through a wooden wall. The wall just has a big hole, there's plenty of clearance. From there, it goes to an underground baffled pit, thence through a 3" plastic vertical stack. All particulates are captured underground. In winter, a bit of steam exits in the exhaust. In dry weather, nothing is seen. the exhaust is quieter than the mechanical noise.
@ Tanman...........our Dursley 6/1 is in an engine room in my shop. It's bolted to a large concrete block. The exhaust exits through the wall. I will try to describe the method..... Exhaust exits the engine via a straight length of 2" automotive exhaust pipe. About a foot from the engine is a length of flexible exhaust pipe. Then more 2" automotive pipe that exits the wall. At the wall exit is a panel of heavy sheet metal about 18" square (it's screwed to the plywood sheathing) with the pipe going through the centre.....loosely fit. Riveted to the panel is a 1 gallon paint can with its lid on, so it is sealed at both ends except the holes for the pipe. The holes in the can fit the pipe closely and are sealed with high temp caulking......the exhaust pipe goes through that and out into a muffler made of concrete block. the sheet metal does not got and it all has been working quite well for about a year.........Does not rattle or vibrate.
Sounds a bit shade tree, but looks quite fine and works.
Of course, YMMV