Steve, you can create a scene of different resolutions but at one point or another it will be squeezed down to two 1920 x 1080 outputs (or whatever your hardware is set too) unless you are using a virtual window but there you would lose a lot of the render capabilities on the hardware. I have a screen that is 3808x1092 that I feed via a tile mapper. I have defined all my scenes to be that size. When the two SDI 1920 x 1080 feeds actually get to the board the board stitches them back together as full frame (3808x1092) by stretching to fit and all the circles come out circles and my squares come out squares. If I were to do the same with a 3840 x 1080 scene then my shapes would have some distortion.
I also employ the custom scene size and virtual windows in order to drive some ribbon boards but I can not remember the dimensions on the final scene for that. 3 scenes for each individual ribbon scene all executed via render views with pretty good success.
As a side note, I have had some issues simul-rolling clips in tile mapper mode. I have some inconsistent results with looping videos but when playing a single video through there is not much of an issue. When I try to loop a video with audio or switch scenes with videos without clearing the frame buffer I run into issues. I have not attempted this recently as I am in the middle of a season now and will wait for post season to play with it and the situation may have improved but clearing the output buffer by hitting escape a bunch of times really fast usually did the trick if things got out of wack.
#XPression