Holy Toledo--the new MESS is great. MESS is so very close to being my emulator of choice for most of the console platforms just because MAME's video output is so vastly superior to every other emulator's.
Symphony of the Night was letterboxed, and with MAME/MESS's video slider options, you can turn off keep aspect ratio and stretch the screen vertically so there's no dead space. It's almost exactly 16:10.
It looks glorious. Thanks for the work on PS1 in MESS.