I got two new locomotives today. An Athearn RTR AC4400 and a Proto 2000 SW9/1200. I had a problem with the AC4400. It runs around 18" radius curves just fine all day long. The rub was when it came to pulling a train. It did all right through the curves until it came to one to makes an 'S'. At this point it yanked the first car off track. An investigation revealed that because of the long end throw on the locomotive the rigid coupler pocket wouldn't allow the coupler to swing very much. So out came the Dremel with a cut-off disk. I opened up the rear pilot and modified the coupler pocket so the coupler can swin 45 degrees both ways. Now it has no problem pulling a train around the layout. A minor problem was the light weight out of the box. I packed the top of the shell with Rose-Art modeling clay, which increased the weight nicely. No more weight problem. This is a scanned view of the AC4400 This a pic of it on the layout. And here's a scan of the SW1200. It's being repainted for KCS.