I've picked this engine up and set it down a number of times so far, and I definitely believe in the idea of stepping away from something like this when I seem to reach a dead end or frustration starts to set in... I'd much rather take my time and come back with a fresh mind than end up breaking something. At the same time I enjoy a good challenge sometimes, and this seemed like a good one to tinker with and see if I could improve some of the functional weaknesses these have...
When I ran it a few times after receiving it I was definitely impressed with how smooth and nice it ran including slowly. But it's weaknesses were readily apparent too... The tether / drawbar arrangement, less than impressive sounds, and it also seemed like the tender trucks were really stiff to swivel and turn. These are all things I'm looking at trying to improve upon. The disassembly process has been really interesting so far, seeing exactly how these are put together. I did a lot of searching thinking someone has surely done a writeup or video of upgrading these and fixing some of their problems, but was surprised I was able to find relatively little about these in that regard.