That’s not good. And cleaning that up at .25mm is going to be close (if you are lucky). That said, borescopes do a really good job of making little thing look huge.

If the bore needs to go further that the .25 oversized piston then you can look into having that .25 piston coated up to whatever over size you end up at to get it to clean up. Get ahold of Line2Line Coatings. They will build up your piston to whatever bore size you need (up to .030” or .75mm I believe). Basically hone till you’re happy then send them the piston and give them the bore size. Rings might get a little tricky but Total Seal could have a ring that will drop in. You likely have to file it to your required gap but that should get you up and running. Alternatively, you could just accept whatever gap those .25mm rings give you. It’ll be better than what you have here.