change the game aspect ratio on PS Vita ?

[lululock]

Hi,
Just tested PlutoBoy on my PS Vita. It works as expected but the image is stretched to fit the PS Vita's screen, which feels wrong. I dunno if there's a way to set that on the PS Vita version, especially since the last time the code was updated to run on the PS Vita was 2 years ago, I don't find much information. There's no menu, only the ROM selection screen, and no way to set anything.

That could be nice to have an option like there was on the original Game Boy Advance when you played a Game Boy (Color) game : you press L and R to switch between the "screen fit" mode and the "original size" mode.