Aircraft models in Ace Combat X, and modding possibilities.

[LunaMoo]

If you use texture scaling, textures are dumped with it, so if you want clear textures, disable upscaling and remove already dumped textures affected by it, then reload the game in place where they show up. PPSSPP should skip scaling replaced elements, so it shouldn't really double, then again most scaling algorithms can be used on top of each other, so it really doesn't matter.

What matters through is that upscaling filters never really look great with all of the graphics in the first place, so for best results you really have to spend some time to re-draw or at least correct some details and shapes, it doesn't always need an artist, sometimes using simple geometry and/or grabbing some free graphics of the net is enough. Maybe even more stuff can be replaced without much skills, like maps itself if they're based on real places, could be replaced by some higher res satellite pics. It all takes time through, so probably not worth unless you get help from some active community if this game/series has one.

As for 60fps stuff, in case you missed it, Kabuto_Kun replied to you in his lenghty post linking to this, so most of the work on it already done in the past. But yeah correcting the speed of everything is the bothersome and time consuming part about making such patches and seems like that one will also need more work.