We know that with cospefogo, how was the original screen, how it is set exactly in Xport emus, etc...
don't spend too much time by looking at the original system spec in wikipedia (and sometimes it's wrong in wikipedia), plus, even if you know exactly the original screen, there are some weird things in our xbox emus:
for example, the original neo geo output is 302*224; so in a sdtv, on fba xxx, the correct value should be 608*448....
lost, we don't know why, but the screen valu in fba, if you don't want any distortions must be 608*452!
Don't make smoke with your brain, there is only one way to check this:
Check with the games in your xbox emus!
- to be sure my snes screen is accurate i use "toys" (horizontal and vertical lines in the 1st level floor)512*478= no distortions! cool i can enjoy all the sprites like they was originally designed by the artists!
- for nes, i check the level 1.1 mountain (a beautifull 45° line),512*448 IS PERFECT for nes
- for genesis i check with "light crusader", or sonic 1
- for pc engine, sidearms is great
- for game boy, mario land is a good game to check
- atari st, pacmania
- gba, zelda minish cap
- neo geo (fbaxxx) view point is perfect
etc....
The best (and only way to be sure) is to launch a game and set our values, you will see the game will play without any distortions.
You had (minor) problems with medna pce in 720p right? for wich game? Is it the only emu you have encountered a little distortion?