FJ I was thinking the same!
Caleb is a tummy sleeper and has been since 4 months. I ended up putting in two long boosters into a BBB and folded them so there was more fabric at the front and I also upsized covers so there was extra coverage at the front. I'm talking super high on his waist rather that just covering the nappy. The cover I got was a Stacinator Malden Mills cover. It was enormous but I'm still using it now!