Replacing fademasks

I'm trying to replace the fademasks (FADE****), but upon entering the game with the file loaded, the console outputs this everytime a screen fade happens:

SRB2 Console said:

WARNING: Fade mask lump FADE**** of incorrect size, ignored

Click to expand...

...with the "****" being the fade number. This happens with all of them. From what I've observed, all of the fades are in the Doom flat format, but exporting them all to PNG shows that they are not in the correct size to be a flat. This struck me as odd, and I'd appreciate any help in creating these lumps correctly.

Thanks!

Fade masks are handled like flats in format, yes. But they do not use powers of 2 in both dimensions for sizes, they use 320x200 or multiples/fractions of those dimensions. They also are not actually flats, so don't place them within F_START and F_END or whatever.

https://wiki.srb2.org/wiki/User:Monster_Iestyn/Screen_fades <--- I've been working on a page for them for a while now; hopefully when it's done it'll be in the mainspace wiki.