I’m not sure how large the area is that pops up, maybe 10nm. before when I geo converted without masks, it was small area, maybe a few tiles, at a time as I fly closer. I’ve decided since there isn’t a fix for scenery popping in the distance, I will probably just live with it. You might try doing a smaller area as a test. I convert 60nm x 135nm, still takes a long time to convert.