Is it possible to create a separate run type where the goal is to create the biggest possible ball for the given level? Just curious.

There isn't much interest for this in the speedrunning community, and honestly max size isn't really a speedrun at all. There are some players who have uploaded max size attempts to youtube, you can find some on this channel: https://www.youtube.com/user/ThumbsOfSteel74/videos. I doubt that we would make a category on here for this due to lack of interest, but if you're thinking of attempting some feel free to join the discord to post the videos or ask questions.

Ok thanks