@ian57 True... but my understanding (from the "manual") was that these settings were for if your display isn't recognised or displaying incorrectly... so as it was displaying correctly for everything - the Recalbox interface, every emulator - except for one emulator, and only one aspect of that emulator, it seemed like the problem with the one emulator was what needed fixing.
It was an insidious problem... and I'm glad to have had the help from you guys to fix it.