Howdy Magus!
I use a simple resolution extension plugin for larger animation sheets. Quite a few MV users use this technique to get around the engine's hardcoded limitation; since MV doesn't support native VFX like MZ, one of the only ways to get specific visual looks is to abuse the animation system.
Like most, I love being able to purchase custom VFX for my games, but short of re-rendering in Effekseer it's hard finding peeps who sell VFX sheets in a larger size. I try to look for oversized sheet VFX to purchase then downscale them as needed in an image editor. I absolutely love the clean look of your VFX and would be more than happy to pay a premium for larger exports of your sheets; I'm sure a lot of other folks would too!
x398px would be a godsend, honestly; I understand it might seem odd at a glance, but it makes the sheets much more viable for higher resolution MV games or games that use large battlers.
Here's an example of a x512 x 60fps animation in MV; (This is STUPID large, but serves as a demonstration. In a final version, the sheet would be cut into multiple animation sequences to reduce memory load.)
