Large steam engine swings different on a curve

That's an excellent point. There are a couple of reasons for locomotives to have a different overhang going forward or backward. There's quite a bit of side-to-side motion ("slop") in an 0 gauge locomotive on its track. The force of the drive wheels can push the body one way forward, the other in reverse. The other thing is that protrusions such as the corner of the cab can just glance off the scenery unnoticed in forward, but hang up in reverse because the corner will snag. I have an MTH 4-12-2 and some articulated engines, so I have to be careful about that too. Another potential problem child is Lionel's new 86-foot boxcar. I bet that has plenty of overhang on the inside of a curve. 

I experienced the same thing with several locos, including the 9000: Mine also overhangs differently going forward versus backward.  And you may have noticed what I did, also: mine does that (overhang differently) differently when pulling/pushing a load or just running by itself.  A long train behind it changes how it overhangs on curves.

The Legacy 9000 is the worst I have seen with regard to "track problems"    In addition to that overhang difference, mine was sensitive to track incline ramp-in: I had to re-adjust two places where I change slop of the track going into and out of an uphill climb: I used a Big Boy to test the track as I laid it down and assumed if it made it over the track, anything else would, and i was right except for Mr. 9000.  I suppose given the twelve drivers, it is only expected its sensitive.  

Still, I like the loco a lot.  Nice, big steamer.  Yes!

The PRR Duplex exhibits the same phenomena.

Its long rigid wheel base extends the cab out as much as the pilot.

Its a REAL layout killer in forward and reverse!

My wife bought me the Scale MTH J. It was cataloged to run on O-42 curves but by the time I got it that was changed to O-54. The folks at MTH told me that when the item came in from China they found it could no back through O-42 switches perfectly, though it ran fine forward. For this reason they had to re-class  it as O-54.

It seems there is a lot more of this in our hobby then I thought.

Oh well, I still love the engine.  

The 9000 class was the largest rigid frame locomotive built and even UP restricted where they operated due to track restrictions.

Mine operate on 0-140 and they look like heck.  Can't imagine this one on 072!  Imagine there is a lot of overhang by the cab.

But, what a fantastic locomotive!  The Legacy version is awesome.  Even the TMCC one is nice if you can get past the 2 chuffs.

Have fun with your locomotive and enjoy it.

one reason to now use 6" centers for track work instead of the old standard of 4.5"

I think most of my steamers take a wider arc in reverse.  I noticed that part of a rock formation on my platform (about the same height as the cab roof) had turned white after I got a MTH RK K4s.  So I scraped off a bunch of the hydrocal for clearance and applied wash.  Then I got a MTH RK 4-8-4 and it cleared…till I reversed thru the curve.  So now there’s a white spot in the rock face again.

I am happy with my 9000 engine. Lionel auto racks being my longest car going forward I have a bit more then a 1/4 of an inch clearance on the curves. I will just make sure not to go backwards. It is a engine that will point out your bad track areas...............Paul 

Another item with serious clearance issues is the Schnabel car. It's wider on one side than the other because of a protruding detail part. I once cleaned off a signal on the biggest main line of our museum layout with mine. I turned the car the other way and it was fine - there was more clearance on the other side of the track. 

Maybe I should put a Schnabel car behind a UP 9000 and add a new Lionel 86' boxcar as the car that carries the related equipment when they do a Schnabel move. And/or an Atlas 89' flatcar with a couple of containers. That would be something to see on the curves!

0-72 and 0-54 will give you 9" clearance if you lay them concentrically. I have concentric 0-63 and 0-72 on my layout, so I can't run anything on the inner main if I'm running the very longest engines and cars on the outer. It doesn't matter that much in the real world, since my layout is pretty small and I run the big stuff at the toy train museum and stick to smaller equipment at home. I have the 0-72 so I can test run anything in my collection at home without having to drive across town to the museum. 

I have the MTH PS3 version, and it's just the same way: a non-articulated that is nearly as bad as the worst articulated as to stick out on curves, and it shifts a bit in backward and forward like the 9000.  On both locos, I think that is a function of the locatio of the traction tires and how they provide toque in curves.  

I bought the S-1 mostly because I wanted one on display in my tranroom's "power wall" of big steamers, and I bought it knowing I would seldom run it.  Beyond the aforementioned "layout wrecking" stock out, it is so big it looks like it is the wrong scale almost, like maybe it is 1:43, not 1:48.  

Still, I wouldn't give it up.  An iconic loco.

More is better with respect to clearances when you build a layout.