2 Screens Fullscreen Issue

Hey guys, I have a problem with the mockup I created. It has exactly the size of two screens on top of each other (1920x2160) and I need to view it on a certain setup now that has exactly two such screens on top of each other. The problem is: Previewing such a mockup in Firefox or Chrome makes it impossible to watch it without a frame or a scrollbar. Are there alternatives or plugins that you know of, which I could use?