your final image will need to be 3,600x24,000 pixels to print at 200pixels-per inch, which is adequate for a print this size. I'd recommend doing the 130x867 method, and zooming in to adjust details. You can also make the scene in a normal canvas and use the pan tool and top-down views to make sure verything is where it need to be, then just make a new document with the right size and merge the other scene file. Adjusting the aspect ratio in the original scene will distort everything, that's why you will need to merge. It's true that at that wide of an agle you will see edge distortions. The best way to fix this is to move the camera further back by a foctor of three and then zoom in. It operates on the telephoto principle in that because the camera is further back, the distance between the camera and each area of the scene is more equal than when it was closer. Then just get ready for a long render :)