How can I add custom resolutions and/or change scaling?

[BuyagaDodzyo]

Have prepackaged mod files in which has "SGD2Res.dll", "SGD2Res.mpq" and "SGD2Resolution.json" files included. I figured out that in "SGD2Resolution.json" we have:
"Ingame Resolutions": [ "640x480", "800x600", "1280x720"
Which meaned that game scale to "1280x720" after character loaded. If my goal are to have something between "1280x720" and "800x600" I need just add there propper numbers? Am I correct?
I don't find about it enywhere and f*ck with those files long enough to ask before I broke something and be forced to check all files to make this mod launchable again. Please help.