Use my Aperture with: shadow_mask_usize 0.625000 shadow_mask_vsize 0.781250
Its important to use this settings for accurate ratio.
I want to mention that shadow_mask_x_count has a BUG. If I set it to 10 there are LESS actual pixels on the screen. The last few are CHOPPED on the right as you can see in the picture. On the contrary shadow_mask_Y_count IS pixel perfect. if you set it to 10 it actually show 10 pictures.
Also its important to mention that Mame original AND my Aperture is doubled. If you set shadow_mask_x_count and shadow_mask_y_count to 320x240 its actually 640x480.
So for Mortal Kombat set it to 200x127 NOT 400x254, this applies to the original mame aperture.
P.S I am not sure if I'm in the right forum for this. Oh, well...