I'm not gonna get penalized for putting a checkpoint in my level, will I? I've played some of the other levels, and I didn't see anyone else using checkpoints from what I played so far. I did test it and you can reasonably beat the level in less than 100 seconds, so that part shouldn't be an issue.
I don't think the inclusion of a checkpoint should result in a level getting penalized. In retrospect, I realized checkpoints are a lot more niche under a short timer.