Using a custom viewport with retropie
I have retropie (pi 3 model b)running mame games in vertical format and it's working pretty well. It's powering an arcade machine with a cardboard bezel around the monitor (which fits the viewable area of the monitor exactly). What I'd like to do is upgrade to a better IPS LED monitor (better viewing angles, brighter, etc); however the monitor is larger than the cardboard bezel and I'm going to want to scale the used screen to just the area covered by the bezel.
It looks doable by setting up a custom viewport in the overall /boot/config.txt file. Before I go and purchase the monitor I just wanted to ask if anyone else has experience doing this.