6.5'x2' Reduced Inglenook?

If you are not dead set on box cars, some tank cars and covered hoppers are slightly shorter.

1. Ore cars are even shorter yet! I have a bunch stashed away for a steel themed 'nook.

2. Are you doing this for modelling sake, or for the switching challenge? If the latter, consider a schematic with a spur off to the right and the left. (fork shape) The first spur serves as the long track, and the second and center serves as the short tracks. You might have to artificially set the length of the center track. 

A 44 Tonner would be good for this

I was able to do it in about 10 feet and I can mix 40 and 50 footers.

If you used ore cars, 2 bay hoppers, something short like that, and then a 44 tonner, or better yet a trackmobile, i think you could shrink it some more. Cant use too tight of a switch radius though or you wont be able to get the couplers aligned to couple and uncouple. 

I would love to grab one of MTH's 44 tonners for this project, although that is a bit outside of my budget for the foreseeable future. The K-Line S-2 isn't my favorite locomotive, it just happens to be what I have currently. Same with the boxcars. I'm not married to them, and those I could replace if needed, but I have them (and like seeing the various paint jobs).

I do like the tank car idea, provided that I could mix up the schemes a bit. Although more realistic, having to go from one identical car to the next reading off numbers to find the one that needs to be moved is not super appealing. I am less interested in the ore cars/hoppers, though not really for any good reason.

It should be noted that my objective wasn't to make the smallest possible O-gauge switching puzzle, but was to design something that will keep me more interested than the tabletop oval while fitting the space that I have. But feel free to keep that side of the discussion going. I'll even add this: A trackmobile, although tiny, would dictate more modern rolling stock if keeping everything in the same period. A K-Line Plymouth switcher would be a better fit. 

Greg Nagy posted:

1. Ore cars are even shorter yet! I have a bunch stashed away for a steel themed 'nook.

2. Are you doing this for modelling sake, or for the switching challenge? If the latter, consider a schematic with a spur off to the right and the left. (fork shape) The first spur serves as the long track, and the second and center serves as the short tracks. You might have to artificially set the length of the center track. 

Both, sort of. My background is HO, and I would like to get back into doing more realistic modeling (albeit with the trouble-free running I've found with 3-rail track). That said, if I can pack in a little more entertainment I would consider it.

What would be the difference with having the long track be a spur off to the side?